Improvements in psql hooks for variables

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a9a2fdb..61b2304 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -254,7 +254,7 @@ exec_command(const char *cmd,
 		if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
 		{
 			reuse_previous =
-				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
+				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix, NULL) ?
 				TRI_YES : TRI_NO;
 
 			free(opt1);
@@ -1548,7 +1548,7 @@ exec_command(const char *cmd,
 												 OT_NORMAL, NULL, false);
 
 		if (opt)
-			pset.timing = ParseVariableBool(opt, "\\timing");
+			pset.timing = ParseVariableBool(opt, "\\timing", NULL);
 		else
 			pset.timing = !pset.timing;
 		if (!pset.quiet)
@@ -2660,7 +2660,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		if (value && pg_strcasecmp(value, "auto") == 0)
 			popt->topt.expanded = 2;
 		else if (value)
-			popt->topt.expanded = ParseVariableBool(value, param);
+			popt->topt.expanded = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.expanded = !popt->topt.expanded;
 	}
@@ -2669,7 +2669,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "numericlocale") == 0)
 	{
 		if (value)
-			popt->topt.numericLocale = ParseVariableBool(value, param);
+			popt->topt.numericLocale = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.numericLocale = !popt->topt.numericLocale;
 	}
@@ -2724,7 +2724,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "t") == 0 || strcmp(param, "tuples_only") == 0)
 	{
 		if (value)
-			popt->topt.tuples_only = ParseVariableBool(value, param);
+			popt->topt.tuples_only = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.tuples_only = !popt->topt.tuples_only;
 	}
@@ -2756,7 +2756,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 			popt->topt.pager = 2;
 		else if (value)
 		{
-			if (ParseVariableBool(value, param))
+			if (ParseVariableBool(value, param, NULL))
 				popt->topt.pager = 1;
 			else
 				popt->topt.pager = 0;
@@ -2778,7 +2778,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "footer") == 0)
 	{
 		if (value)
-			popt->topt.default_footer = ParseVariableBool(value, param);
+			popt->topt.default_footer = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.default_footer = !popt->topt.default_footer;
 	}
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 7ce05fb..9dcfc0a 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -786,43 +786,59 @@ showVersion(void)
  * This isn't an amazingly good place for them, but neither is anywhere else.
  */
 
-static void
+/*
+ * Hook to set an internal flag from a user-supplied string value.
+ * If the syntax is correct, affect *flag and return true.
+ * Otherwise, keep *flag untouched and return false.
+ */
+static bool
+generic_boolean_hook(const char *newval, const char* varname, bool *flag)
+{
+	bool isvalid;
+	bool val = ParseVariableBool(newval, varname, &isvalid);
+	if (isvalid)
+		*flag = val;
+	return isvalid;
+}
+
+static bool
 autocommit_hook(const char *newval)
 {
-	pset.autocommit = ParseVariableBool(newval, "AUTOCOMMIT");
+	return generic_boolean_hook(newval, "AUTOCOMMIT", &pset.autocommit);
 }
 
-static void
+static bool
 on_error_stop_hook(const char *newval)
 {
-	pset.on_error_stop = ParseVariableBool(newval, "ON_ERROR_STOP");
+	return generic_boolean_hook(newval, "ON_ERROR_STOP", &pset.on_error_stop);
 }
 
-static void
+static bool
 quiet_hook(const char *newval)
 {
-	pset.quiet = ParseVariableBool(newval, "QUIET");
+	return generic_boolean_hook(newval, "QUIET", &pset.quiet);
 }
 
-static void
+static bool
 singleline_hook(const char *newval)
 {
-	pset.singleline = ParseVariableBool(newval, "SINGLELINE");
+	return generic_boolean_hook(newval, "SINGLELINE", &pset.singleline);
 }
 
-static void
+static bool
 singlestep_hook(const char *newval)
 {
-	pset.singlestep = ParseVariableBool(newval, "SINGLESTEP");
+	return generic_boolean_hook(newval, "SINGLESTEP", &pset.singlestep);
 }
 
-static void
+static bool
 fetch_count_hook(const char *newval)
 {
 	pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
+	return true;
 }
 
-static void
+static bool
 echo_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -837,39 +853,52 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "ECHO", "none");
-		pset.echo = PSQL_ECHO_NONE;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "ECHO");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 echo_hidden_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
 	else if (pg_strcasecmp(newval, "noexec") == 0)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
-	else if (ParseVariableBool(newval, "ECHO_HIDDEN"))
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ECHO_HIDDEN", &isvalid);
+		if (!isvalid)
+			return false; /* ParseVariableBool printed msg */
+		pset.echo_hidden = val ? PSQL_ECHO_HIDDEN_ON : PSQL_ECHO_HIDDEN_OFF;
+	}
+	return true;
 }
 
-static void
+static bool
 on_error_rollback_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
 	else if (pg_strcasecmp(newval, "interactive") == 0)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
-	else if (ParseVariableBool(newval, "ON_ERROR_ROLLBACK"))
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ON_ERROR_ROLLBACK", &isvalid);
+		if (isvalid)
+			pset.on_error_rollback = val ? PSQL_ERROR_ROLLBACK_ON : PSQL_ERROR_ROLLBACK_OFF;
+		else
+			/* ParseVariableBool printed msg if needed */
+			return false;
+	}
+	return true;
 }
 
-static void
+static bool
 comp_keyword_case_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -884,13 +913,14 @@ comp_keyword_case_hook(const char *newval)
 		pset.comp_case = PSQL_COMP_CASE_LOWER;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "COMP_KEYWORD_CASE", "preserve-upper");
-		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "COMP_KEYWORD_CASE");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 histcontrol_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -905,31 +935,35 @@ histcontrol_hook(const char *newval)
 		pset.histcontrol = hctl_none;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "HISTCONTROL", "none");
-		pset.histcontrol = hctl_none;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "HISTCONTROL");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 prompt1_hook(const char *newval)
 {
 	pset.prompt1 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt2_hook(const char *newval)
 {
 	pset.prompt2 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt3_hook(const char *newval)
 {
 	pset.prompt3 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 verbosity_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -942,16 +976,17 @@ verbosity_hook(const char *newval)
 		pset.verbosity = PQERRORS_VERBOSE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "VERBOSITY", "default");
-		pset.verbosity = PQERRORS_DEFAULT;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "VERBOSITY");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorVerbosity(pset.db, pset.verbosity);
+	return true;
 }
 
-static void
+static bool
 show_context_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -964,13 +999,14 @@ show_context_hook(const char *newval)
 		pset.show_context = PQSHOW_CONTEXT_ALWAYS;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "SHOW_CONTEXT", "errors");
-		pset.show_context = PQSHOW_CONTEXT_ERRORS;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "SHOW_CONTEXT");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorContextVisibility(pset.db, pset.show_context);
+	return true;
 }
 
 
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index f43f418..24ca750 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -86,12 +86,16 @@ GetVariable(VariableSpace space, const char *name)
  *
  * "name" is the name of the variable we're assigning to, to use in error
  * report if any.  Pass name == NULL to suppress the error report.
+ *
+ * "*valid" reports whether "value" was syntactically valid, unless valid == NULL
  */
 bool
-ParseVariableBool(const char *value, const char *name)
+ParseVariableBool(const char *value, const char *name, bool *valid)
 {
 	size_t		len;
 
+	if (valid)
+		*valid = true;
 	if (value == NULL)
 		return false;			/* not set -> assume "off" */
 
@@ -116,10 +120,16 @@ ParseVariableBool(const char *value, const char *name)
 		return false;
 	else
 	{
-		/* NULL is treated as false, so a non-matching value is 'true' */
+		/*
+		 * NULL is treated as false, so a non-matching value is 'true'.
+		 * A caller that cares about syntactic conformance should
+		 * check *valid to know whether the value was recognized.
+		 */
 		if (name)
-			psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-					   value, name, "on");
+			psql_error("unrecognized value \"%s\" for \"%s\": boolean expected\n",
+					   value, name);
+		if (valid)
+			*valid = false;
 		return true;
 	}
 }
@@ -205,13 +215,19 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 	{
 		if (strcmp(current->name, name) == 0)
 		{
-			/* found entry, so update */
-			if (current->value)
-				free(current->value);
-			current->value = pg_strdup(value);
+			/* found entry, so update, unless a hook returns false */
+			bool confirmed = true;
 			if (current->assign_hook)
-				(*current->assign_hook) (current->value);
-			return true;
+			{
+				confirmed = (*current->assign_hook) (value);
+			}
+			if (confirmed)
+			{
+				if (current->value)
+					free(current->value);
+				current->value = pg_strdup(value);
+			}
+			return confirmed;
 		}
 	}
 
@@ -248,7 +264,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 		{
 			/* found entry, so update */
 			current->assign_hook = hook;
-			(*hook) (current->value);
+			(void)(*hook) (current->value); /* ignore return value */
 			return true;
 		}
 	}
@@ -260,7 +276,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(*hook) (NULL);
+	(void)(*hook) (NULL);		/* ignore return value */
 	return true;
 }
 
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index d7a05a1..9836fc5 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -20,7 +20,7 @@
  * Note: if value == NULL then the variable is logically unset, but we are
  * keeping the struct around so as not to forget about its hook function.
  */
-typedef void (*VariableAssignHook) (const char *newval);
+typedef bool (*VariableAssignHook) (const char *newval);
 
 struct _variable
 {
@@ -35,7 +35,7 @@ typedef struct _variable *VariableSpace;
 VariableSpace CreateVariableSpace(void);
 const char *GetVariable(VariableSpace space, const char *name);
 
-bool		ParseVariableBool(const char *value, const char *name);
+bool		ParseVariableBool(const char *value, const char *name, bool *valid);
 int ParseVariableNum(const char *val,
 				 int defaultval,
 				 int faultval,

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a9a2fdb..61b2304 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -254,7 +254,7 @@ exec_command(const char *cmd,
 		if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
 		{
 			reuse_previous =
-				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
+				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix, NULL) ?
 				TRI_YES : TRI_NO;
 
 			free(opt1);
@@ -1548,7 +1548,7 @@ exec_command(const char *cmd,
 												 OT_NORMAL, NULL, false);
 
 		if (opt)
-			pset.timing = ParseVariableBool(opt, "\\timing");
+			pset.timing = ParseVariableBool(opt, "\\timing", NULL);
 		else
 			pset.timing = !pset.timing;
 		if (!pset.quiet)
@@ -2660,7 +2660,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		if (value && pg_strcasecmp(value, "auto") == 0)
 			popt->topt.expanded = 2;
 		else if (value)
-			popt->topt.expanded = ParseVariableBool(value, param);
+			popt->topt.expanded = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.expanded = !popt->topt.expanded;
 	}
@@ -2669,7 +2669,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "numericlocale") == 0)
 	{
 		if (value)
-			popt->topt.numericLocale = ParseVariableBool(value, param);
+			popt->topt.numericLocale = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.numericLocale = !popt->topt.numericLocale;
 	}
@@ -2724,7 +2724,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "t") == 0 || strcmp(param, "tuples_only") == 0)
 	{
 		if (value)
-			popt->topt.tuples_only = ParseVariableBool(value, param);
+			popt->topt.tuples_only = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.tuples_only = !popt->topt.tuples_only;
 	}
@@ -2756,7 +2756,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 			popt->topt.pager = 2;
 		else if (value)
 		{
-			if (ParseVariableBool(value, param))
+			if (ParseVariableBool(value, param, NULL))
 				popt->topt.pager = 1;
 			else
 				popt->topt.pager = 0;
@@ -2778,7 +2778,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "footer") == 0)
 	{
 		if (value)
-			popt->topt.default_footer = ParseVariableBool(value, param);
+			popt->topt.default_footer = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.default_footer = !popt->topt.default_footer;
 	}
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 7ce05fb..ba094f0 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -786,43 +786,68 @@ showVersion(void)
  * This isn't an amazingly good place for them, but neither is anywhere else.
  */
 
-static void
+/*
+ * Hook to set an internal flag from a user-supplied string value.
+ * If the syntax is correct, affect *flag and return true.
+ * Otherwise, keep *flag untouched and return false.
+ */
+static bool
+generic_boolean_hook(const char *newval, const char* varname, bool *flag)
+{
+	bool isvalid;
+	bool val = ParseVariableBool(newval, varname, &isvalid);
+	if (isvalid)
+		*flag = val;
+	return isvalid;
+}
+
+static bool
 autocommit_hook(const char *newval)
 {
-	pset.autocommit = ParseVariableBool(newval, "AUTOCOMMIT");
+	return generic_boolean_hook(newval, "AUTOCOMMIT", &pset.autocommit);
 }
 
-static void
+static bool
 on_error_stop_hook(const char *newval)
 {
-	pset.on_error_stop = ParseVariableBool(newval, "ON_ERROR_STOP");
+	return generic_boolean_hook(newval, "ON_ERROR_STOP", &pset.on_error_stop);
 }
 
-static void
+static bool
 quiet_hook(const char *newval)
 {
-	pset.quiet = ParseVariableBool(newval, "QUIET");
+	return generic_boolean_hook(newval, "QUIET", &pset.quiet);
 }
 
-static void
+static bool
 singleline_hook(const char *newval)
 {
-	pset.singleline = ParseVariableBool(newval, "SINGLELINE");
+	return generic_boolean_hook(newval, "SINGLELINE", &pset.singleline);
 }
 
-static void
+static bool
 singlestep_hook(const char *newval)
 {
-	pset.singlestep = ParseVariableBool(newval, "SINGLESTEP");
+	return generic_boolean_hook(newval, "SINGLESTEP", &pset.singlestep);
 }
 
-static void
+static bool
 fetch_count_hook(const char *newval)
 {
-	pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
+	bool valid;
+	int value = ParseCheckVariableNum(newval, -1, &valid);
+	if (valid)
+		pset.fetch_count = value;
+	else
+	{
+		psql_error("invalid value \"%s\" for \"%s\"\n",
+				   newval, "FETCH_COUNT");
+		return false;
+	}
+	return true;
 }
 
-static void
+static bool
 echo_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -837,39 +862,52 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "ECHO", "none");
-		pset.echo = PSQL_ECHO_NONE;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "ECHO");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 echo_hidden_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
 	else if (pg_strcasecmp(newval, "noexec") == 0)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
-	else if (ParseVariableBool(newval, "ECHO_HIDDEN"))
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ECHO_HIDDEN", &isvalid);
+		if (!isvalid)
+			return false; /* ParseVariableBool printed msg */
+		pset.echo_hidden = val ? PSQL_ECHO_HIDDEN_ON : PSQL_ECHO_HIDDEN_OFF;
+	}
+	return true;
 }
 
-static void
+static bool
 on_error_rollback_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
 	else if (pg_strcasecmp(newval, "interactive") == 0)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
-	else if (ParseVariableBool(newval, "ON_ERROR_ROLLBACK"))
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ON_ERROR_ROLLBACK", &isvalid);
+		if (isvalid)
+			pset.on_error_rollback = val ? PSQL_ERROR_ROLLBACK_ON : PSQL_ERROR_ROLLBACK_OFF;
+		else
+			/* ParseVariableBool printed msg if needed */
+			return false;
+	}
+	return true;
 }
 
-static void
+static bool
 comp_keyword_case_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -884,13 +922,14 @@ comp_keyword_case_hook(const char *newval)
 		pset.comp_case = PSQL_COMP_CASE_LOWER;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "COMP_KEYWORD_CASE", "preserve-upper");
-		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "COMP_KEYWORD_CASE");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 histcontrol_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -905,31 +944,35 @@ histcontrol_hook(const char *newval)
 		pset.histcontrol = hctl_none;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "HISTCONTROL", "none");
-		pset.histcontrol = hctl_none;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "HISTCONTROL");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 prompt1_hook(const char *newval)
 {
 	pset.prompt1 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt2_hook(const char *newval)
 {
 	pset.prompt2 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt3_hook(const char *newval)
 {
 	pset.prompt3 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 verbosity_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -942,16 +985,17 @@ verbosity_hook(const char *newval)
 		pset.verbosity = PQERRORS_VERBOSE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "VERBOSITY", "default");
-		pset.verbosity = PQERRORS_DEFAULT;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "VERBOSITY");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorVerbosity(pset.db, pset.verbosity);
+	return true;
 }
 
-static void
+static bool
 show_context_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -964,13 +1008,14 @@ show_context_hook(const char *newval)
 		pset.show_context = PQSHOW_CONTEXT_ALWAYS;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "SHOW_CONTEXT", "errors");
-		pset.show_context = PQSHOW_CONTEXT_ERRORS;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "SHOW_CONTEXT");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorContextVisibility(pset.db, pset.show_context);
+	return true;
 }
 
 
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index f43f418..5e68b67 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -86,12 +86,16 @@ GetVariable(VariableSpace space, const char *name)
  *
  * "name" is the name of the variable we're assigning to, to use in error
  * report if any.  Pass name == NULL to suppress the error report.
+ *
+ * "*valid" reports whether "value" was syntactically valid, unless valid == NULL
  */
 bool
-ParseVariableBool(const char *value, const char *name)
+ParseVariableBool(const char *value, const char *name, bool *valid)
 {
 	size_t		len;
 
+	if (valid)
+		*valid = true;
 	if (value == NULL)
 		return false;			/* not set -> assume "off" */
 
@@ -116,10 +120,16 @@ ParseVariableBool(const char *value, const char *name)
 		return false;
 	else
 	{
-		/* NULL is treated as false, so a non-matching value is 'true' */
+		/*
+		 * NULL is treated as false, so a non-matching value is 'true'.
+		 * A caller that cares about syntactic conformance should
+		 * check *valid to know whether the value was recognized.
+		 */
 		if (name)
-			psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-					   value, name, "on");
+			psql_error("unrecognized value \"%s\" for \"%s\": boolean expected\n",
+					   value, name);
+		if (valid)
+			*valid = false;
 		return true;
 	}
 }
@@ -154,6 +164,35 @@ ParseVariableNum(const char *val,
 	return result;
 }
 
+/*
+ * Read numeric variable, or defaultval if it is not set.
+ * Trailing contents are not allowed.
+ * "valid" points to a bool reporting whether the value was valid.
+ */
+int
+ParseCheckVariableNum(const char *val,
+					  int defaultval,
+					  bool *valid)
+{
+	int		result;
+
+	if (!val)
+	{
+		*valid = true;
+		result = defaultval;
+	}
+	else
+	{
+		char	   *end;
+
+		errno = 0;
+		result = strtol(val, &end, 0);
+		*valid = (val[0] != '\0' && errno == 0 && *end == '\0');
+	}
+
+	return result;
+}
+
 int
 GetVariableNum(VariableSpace space,
 			   const char *name,
@@ -205,13 +244,17 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 	{
 		if (strcmp(current->name, name) == 0)
 		{
-			/* found entry, so update */
-			if (current->value)
-				free(current->value);
-			current->value = pg_strdup(value);
-			if (current->assign_hook)
-				(*current->assign_hook) (current->value);
-			return true;
+			/* found entry, so update, unless a hook returns false */
+			bool confirmed = current->assign_hook ?
+							(*current->assign_hook) (value) : true;
+
+			if (confirmed)
+			{
+				if (current->value)
+					free(current->value);
+				current->value = pg_strdup(value);
+			}
+			return confirmed;
 		}
 	}
 
@@ -248,7 +291,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 		{
 			/* found entry, so update */
 			current->assign_hook = hook;
-			(*hook) (current->value);
+			(*hook) (current->value); /* ignore return value */
 			return true;
 		}
 	}
@@ -260,7 +303,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(*hook) (NULL);
+	(void)(*hook) (NULL);		/* ignore return value */
 	return true;
 }
 
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index d7a05a1..38396ba 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -20,7 +20,7 @@
  * Note: if value == NULL then the variable is logically unset, but we are
  * keeping the struct around so as not to forget about its hook function.
  */
-typedef void (*VariableAssignHook) (const char *newval);
+typedef bool (*VariableAssignHook) (const char *newval);
 
 struct _variable
 {
@@ -35,11 +35,14 @@ typedef struct _variable *VariableSpace;
 VariableSpace CreateVariableSpace(void);
 const char *GetVariable(VariableSpace space, const char *name);
 
-bool		ParseVariableBool(const char *value, const char *name);
+bool		ParseVariableBool(const char *value, const char *name, bool *valid);
 int ParseVariableNum(const char *val,
 				 int defaultval,
 				 int faultval,
 				 bool allowtrail);
+int ParseCheckVariableNum(const char *val,
+						  int defaultval,
+						  bool *valid);
 int GetVariableNum(VariableSpace space,
 			   const char *name,
 			   int defaultval,

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a9a2fdb..61b2304 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -254,7 +254,7 @@ exec_command(const char *cmd,
 		if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
 		{
 			reuse_previous =
-				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
+				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix, NULL) ?
 				TRI_YES : TRI_NO;
 
 			free(opt1);
@@ -1548,7 +1548,7 @@ exec_command(const char *cmd,
 												 OT_NORMAL, NULL, false);
 
 		if (opt)
-			pset.timing = ParseVariableBool(opt, "\\timing");
+			pset.timing = ParseVariableBool(opt, "\\timing", NULL);
 		else
 			pset.timing = !pset.timing;
 		if (!pset.quiet)
@@ -2660,7 +2660,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		if (value && pg_strcasecmp(value, "auto") == 0)
 			popt->topt.expanded = 2;
 		else if (value)
-			popt->topt.expanded = ParseVariableBool(value, param);
+			popt->topt.expanded = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.expanded = !popt->topt.expanded;
 	}
@@ -2669,7 +2669,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "numericlocale") == 0)
 	{
 		if (value)
-			popt->topt.numericLocale = ParseVariableBool(value, param);
+			popt->topt.numericLocale = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.numericLocale = !popt->topt.numericLocale;
 	}
@@ -2724,7 +2724,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "t") == 0 || strcmp(param, "tuples_only") == 0)
 	{
 		if (value)
-			popt->topt.tuples_only = ParseVariableBool(value, param);
+			popt->topt.tuples_only = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.tuples_only = !popt->topt.tuples_only;
 	}
@@ -2756,7 +2756,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 			popt->topt.pager = 2;
 		else if (value)
 		{
-			if (ParseVariableBool(value, param))
+			if (ParseVariableBool(value, param, NULL))
 				popt->topt.pager = 1;
 			else
 				popt->topt.pager = 0;
@@ -2778,7 +2778,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "footer") == 0)
 	{
 		if (value)
-			popt->topt.default_footer = ParseVariableBool(value, param);
+			popt->topt.default_footer = ParseVariableBool(value, param, NULL);
 		else
 			popt->topt.default_footer = !popt->topt.default_footer;
 	}
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 7ce05fb..ba094f0 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -786,43 +786,68 @@ showVersion(void)
  * This isn't an amazingly good place for them, but neither is anywhere else.
  */
 
-static void
+/*
+ * Hook to set an internal flag from a user-supplied string value.
+ * If the syntax is correct, affect *flag and return true.
+ * Otherwise, keep *flag untouched and return false.
+ */
+static bool
+generic_boolean_hook(const char *newval, const char* varname, bool *flag)
+{
+	bool isvalid;
+	bool val = ParseVariableBool(newval, varname, &isvalid);
+	if (isvalid)
+		*flag = val;
+	return isvalid;
+}
+
+static bool
 autocommit_hook(const char *newval)
 {
-	pset.autocommit = ParseVariableBool(newval, "AUTOCOMMIT");
+	return generic_boolean_hook(newval, "AUTOCOMMIT", &pset.autocommit);
 }
 
-static void
+static bool
 on_error_stop_hook(const char *newval)
 {
-	pset.on_error_stop = ParseVariableBool(newval, "ON_ERROR_STOP");
+	return generic_boolean_hook(newval, "ON_ERROR_STOP", &pset.on_error_stop);
 }
 
-static void
+static bool
 quiet_hook(const char *newval)
 {
-	pset.quiet = ParseVariableBool(newval, "QUIET");
+	return generic_boolean_hook(newval, "QUIET", &pset.quiet);
 }
 
-static void
+static bool
 singleline_hook(const char *newval)
 {
-	pset.singleline = ParseVariableBool(newval, "SINGLELINE");
+	return generic_boolean_hook(newval, "SINGLELINE", &pset.singleline);
 }
 
-static void
+static bool
 singlestep_hook(const char *newval)
 {
-	pset.singlestep = ParseVariableBool(newval, "SINGLESTEP");
+	return generic_boolean_hook(newval, "SINGLESTEP", &pset.singlestep);
 }
 
-static void
+static bool
 fetch_count_hook(const char *newval)
 {
-	pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
+	bool valid;
+	int value = ParseCheckVariableNum(newval, -1, &valid);
+	if (valid)
+		pset.fetch_count = value;
+	else
+	{
+		psql_error("invalid value \"%s\" for \"%s\"\n",
+				   newval, "FETCH_COUNT");
+		return false;
+	}
+	return true;
 }
 
-static void
+static bool
 echo_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -837,39 +862,52 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "ECHO", "none");
-		pset.echo = PSQL_ECHO_NONE;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "ECHO");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 echo_hidden_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
 	else if (pg_strcasecmp(newval, "noexec") == 0)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
-	else if (ParseVariableBool(newval, "ECHO_HIDDEN"))
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ECHO_HIDDEN", &isvalid);
+		if (!isvalid)
+			return false; /* ParseVariableBool printed msg */
+		pset.echo_hidden = val ? PSQL_ECHO_HIDDEN_ON : PSQL_ECHO_HIDDEN_OFF;
+	}
+	return true;
 }
 
-static void
+static bool
 on_error_rollback_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
 	else if (pg_strcasecmp(newval, "interactive") == 0)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
-	else if (ParseVariableBool(newval, "ON_ERROR_ROLLBACK"))
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ON_ERROR_ROLLBACK", &isvalid);
+		if (isvalid)
+			pset.on_error_rollback = val ? PSQL_ERROR_ROLLBACK_ON : PSQL_ERROR_ROLLBACK_OFF;
+		else
+			/* ParseVariableBool printed msg if needed */
+			return false;
+	}
+	return true;
 }
 
-static void
+static bool
 comp_keyword_case_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -884,13 +922,14 @@ comp_keyword_case_hook(const char *newval)
 		pset.comp_case = PSQL_COMP_CASE_LOWER;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "COMP_KEYWORD_CASE", "preserve-upper");
-		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "COMP_KEYWORD_CASE");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 histcontrol_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -905,31 +944,35 @@ histcontrol_hook(const char *newval)
 		pset.histcontrol = hctl_none;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "HISTCONTROL", "none");
-		pset.histcontrol = hctl_none;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "HISTCONTROL");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 prompt1_hook(const char *newval)
 {
 	pset.prompt1 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt2_hook(const char *newval)
 {
 	pset.prompt2 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt3_hook(const char *newval)
 {
 	pset.prompt3 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 verbosity_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -942,16 +985,17 @@ verbosity_hook(const char *newval)
 		pset.verbosity = PQERRORS_VERBOSE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "VERBOSITY", "default");
-		pset.verbosity = PQERRORS_DEFAULT;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "VERBOSITY");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorVerbosity(pset.db, pset.verbosity);
+	return true;
 }
 
-static void
+static bool
 show_context_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -964,13 +1008,14 @@ show_context_hook(const char *newval)
 		pset.show_context = PQSHOW_CONTEXT_ALWAYS;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "SHOW_CONTEXT", "errors");
-		pset.show_context = PQSHOW_CONTEXT_ERRORS;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "SHOW_CONTEXT");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorContextVisibility(pset.db, pset.show_context);
+	return true;
 }
 
 
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index f43f418..8532af4 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -86,24 +86,28 @@ GetVariable(VariableSpace space, const char *name)
  *
  * "name" is the name of the variable we're assigning to, to use in error
  * report if any.  Pass name == NULL to suppress the error report.
+ *
+ * "*valid" reports whether "value" was syntactically valid, unless valid == NULL
  */
 bool
-ParseVariableBool(const char *value, const char *name)
+ParseVariableBool(const char *value, const char *name, bool *valid)
 {
 	size_t		len;
 
+	if (valid)
+		*valid = true;
 	if (value == NULL)
 		return false;			/* not set -> assume "off" */
 
 	len = strlen(value);
 
-	if (pg_strncasecmp(value, "true", len) == 0)
+	if (len > 0 && pg_strncasecmp(value, "true", len) == 0)
 		return true;
-	else if (pg_strncasecmp(value, "false", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "false", len) == 0)
 		return false;
-	else if (pg_strncasecmp(value, "yes", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "yes", len) == 0)
 		return true;
-	else if (pg_strncasecmp(value, "no", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "no", len) == 0)
 		return false;
 	/* 'o' is not unique enough */
 	else if (pg_strncasecmp(value, "on", (len > 2 ? len : 2)) == 0)
@@ -116,10 +120,16 @@ ParseVariableBool(const char *value, const char *name)
 		return false;
 	else
 	{
-		/* NULL is treated as false, so a non-matching value is 'true' */
+		/*
+		 * NULL is treated as false, so a non-matching value is 'true'.
+		 * A caller that cares about syntactic conformance should
+		 * check *valid to know whether the value was recognized.
+		 */
 		if (name)
-			psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-					   value, name, "on");
+			psql_error("unrecognized value \"%s\" for \"%s\": boolean expected\n",
+					   value, name);
+		if (valid)
+			*valid = false;
 		return true;
 	}
 }
@@ -154,6 +164,35 @@ ParseVariableNum(const char *val,
 	return result;
 }
 
+/*
+ * Read numeric variable, or defaultval if it is not set.
+ * Trailing contents are not allowed.
+ * "valid" points to a bool reporting whether the value was valid.
+ */
+int
+ParseCheckVariableNum(const char *val,
+					  int defaultval,
+					  bool *valid)
+{
+	int		result;
+
+	if (!val)
+	{
+		*valid = true;
+		result = defaultval;
+	}
+	else
+	{
+		char	   *end;
+
+		errno = 0;
+		result = strtol(val, &end, 0);
+		*valid = (val[0] != '\0' && errno == 0 && *end == '\0');
+	}
+
+	return result;
+}
+
 int
 GetVariableNum(VariableSpace space,
 			   const char *name,
@@ -205,13 +244,26 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 	{
 		if (strcmp(current->name, name) == 0)
 		{
-			/* found entry, so update */
-			if (current->value)
-				free(current->value);
-			current->value = pg_strdup(value);
-			if (current->assign_hook)
-				(*current->assign_hook) (current->value);
-			return true;
+			/*
+			 * Found entry, so update, unless a hook returns false.
+			 * The hook needs the value in a buffer with the same lifespan
+			 * as the variable, so allocate it right away, even if it needs
+			 * to be freed just after when the hook returns false.
+			 */
+			char *new_value = pg_strdup(value);
+
+			bool confirmed = current->assign_hook ?
+							(*current->assign_hook) (new_value) : true;
+
+			if (confirmed)
+			{
+				pg_free(current->value);
+				current->value = new_value;
+			}
+			else
+				pg_free(new_value); /* and current->value is left unchanged */
+
+			return confirmed;
 		}
 	}
 
@@ -248,7 +300,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 		{
 			/* found entry, so update */
 			current->assign_hook = hook;
-			(*hook) (current->value);
+			(*hook) (current->value); /* ignore return value */
 			return true;
 		}
 	}
@@ -260,7 +312,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(*hook) (NULL);
+	(void)(*hook) (NULL);		/* ignore return value */
 	return true;
 }
 
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index d7a05a1..38396ba 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -20,7 +20,7 @@
  * Note: if value == NULL then the variable is logically unset, but we are
  * keeping the struct around so as not to forget about its hook function.
  */
-typedef void (*VariableAssignHook) (const char *newval);
+typedef bool (*VariableAssignHook) (const char *newval);
 
 struct _variable
 {
@@ -35,11 +35,14 @@ typedef struct _variable *VariableSpace;
 VariableSpace CreateVariableSpace(void);
 const char *GetVariable(VariableSpace space, const char *name);
 
-bool		ParseVariableBool(const char *value, const char *name);
+bool		ParseVariableBool(const char *value, const char *name, bool *valid);
 int ParseVariableNum(const char *val,
 				 int defaultval,
 				 int faultval,
 				 bool allowtrail);
+int ParseCheckVariableNum(const char *val,
+						  int defaultval,
+						  bool *valid);
 int GetVariableNum(VariableSpace space,
 			   const char *name,
 			   int defaultval,

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a9a2fdb..356467b 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -254,25 +254,30 @@ exec_command(const char *cmd,
 		if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
 		{
 			reuse_previous =
-				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
+				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix, &success) ?
 				TRI_YES : TRI_NO;
-
-			free(opt1);
-			opt1 = read_connect_arg(scan_state);
+			if (success)
+			{
+				free(opt1);
+				opt1 = read_connect_arg(scan_state);
+			}
 		}
 		else
 			reuse_previous = TRI_DEFAULT;
 
-		opt2 = read_connect_arg(scan_state);
-		opt3 = read_connect_arg(scan_state);
-		opt4 = read_connect_arg(scan_state);
+		if (success)			/* do not attempt to connect if reuse_previous argument was invalid */
+		{
+			opt2 = read_connect_arg(scan_state);
+			opt3 = read_connect_arg(scan_state);
+			opt4 = read_connect_arg(scan_state);
 
-		success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
+			success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
 
+			free(opt2);
+			free(opt3);
+			free(opt4);
+		}
 		free(opt1);
-		free(opt2);
-		free(opt3);
-		free(opt4);
 	}
 
 	/* \cd */
@@ -1548,7 +1553,11 @@ exec_command(const char *cmd,
 												 OT_NORMAL, NULL, false);
 
 		if (opt)
-			pset.timing = ParseVariableBool(opt, "\\timing");
+		{
+			bool	newval = ParseVariableBool(opt, "\\timing", &success);
+			if (success)
+				pset.timing = newval;
+		}
 		else
 			pset.timing = !pset.timing;
 		if (!pset.quiet)
@@ -2660,7 +2669,14 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		if (value && pg_strcasecmp(value, "auto") == 0)
 			popt->topt.expanded = 2;
 		else if (value)
-			popt->topt.expanded = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, param, &valid);
+			if (valid)
+				popt->topt.expanded = newval;
+			else
+				return false;
+		}
 		else
 			popt->topt.expanded = !popt->topt.expanded;
 	}
@@ -2668,8 +2684,16 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	/* locale-aware numeric output */
 	else if (strcmp(param, "numericlocale") == 0)
 	{
+
 		if (value)
-			popt->topt.numericLocale = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, param, &valid);
+			if (valid)
+				popt->topt.numericLocale = newval;
+			else
+				return false;
+		}
 		else
 			popt->topt.numericLocale = !popt->topt.numericLocale;
 	}
@@ -2724,7 +2748,14 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "t") == 0 || strcmp(param, "tuples_only") == 0)
 	{
 		if (value)
-			popt->topt.tuples_only = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, param, &valid);
+			if (valid)
+				popt->topt.tuples_only = newval;
+			else
+				return false;
+		}
 		else
 			popt->topt.tuples_only = !popt->topt.tuples_only;
 	}
@@ -2756,10 +2787,11 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 			popt->topt.pager = 2;
 		else if (value)
 		{
-			if (ParseVariableBool(value, param))
-				popt->topt.pager = 1;
-			else
-				popt->topt.pager = 0;
+			bool	valid;
+			bool	on = ParseVariableBool(value, param, &valid);
+			if (!valid)
+				return false;
+			popt->topt.pager = on ? 1 : 0;
 		}
 		else if (popt->topt.pager == 1)
 			popt->topt.pager = 0;
@@ -2778,7 +2810,14 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "footer") == 0)
 	{
 		if (value)
-			popt->topt.default_footer = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, param, &valid);
+			if (valid)
+				popt->topt.default_footer = newval;
+			else
+				return false;
+		}
 		else
 			popt->topt.default_footer = !popt->topt.default_footer;
 	}
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 7ce05fb..ba094f0 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -786,43 +786,68 @@ showVersion(void)
  * This isn't an amazingly good place for them, but neither is anywhere else.
  */
 
-static void
+/*
+ * Hook to set an internal flag from a user-supplied string value.
+ * If the syntax is correct, affect *flag and return true.
+ * Otherwise, keep *flag untouched and return false.
+ */
+static bool
+generic_boolean_hook(const char *newval, const char* varname, bool *flag)
+{
+	bool isvalid;
+	bool val = ParseVariableBool(newval, varname, &isvalid);
+	if (isvalid)
+		*flag = val;
+	return isvalid;
+}
+
+static bool
 autocommit_hook(const char *newval)
 {
-	pset.autocommit = ParseVariableBool(newval, "AUTOCOMMIT");
+	return generic_boolean_hook(newval, "AUTOCOMMIT", &pset.autocommit);
 }
 
-static void
+static bool
 on_error_stop_hook(const char *newval)
 {
-	pset.on_error_stop = ParseVariableBool(newval, "ON_ERROR_STOP");
+	return generic_boolean_hook(newval, "ON_ERROR_STOP", &pset.on_error_stop);
 }
 
-static void
+static bool
 quiet_hook(const char *newval)
 {
-	pset.quiet = ParseVariableBool(newval, "QUIET");
+	return generic_boolean_hook(newval, "QUIET", &pset.quiet);
 }
 
-static void
+static bool
 singleline_hook(const char *newval)
 {
-	pset.singleline = ParseVariableBool(newval, "SINGLELINE");
+	return generic_boolean_hook(newval, "SINGLELINE", &pset.singleline);
 }
 
-static void
+static bool
 singlestep_hook(const char *newval)
 {
-	pset.singlestep = ParseVariableBool(newval, "SINGLESTEP");
+	return generic_boolean_hook(newval, "SINGLESTEP", &pset.singlestep);
 }
 
-static void
+static bool
 fetch_count_hook(const char *newval)
 {
-	pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
+	bool valid;
+	int value = ParseCheckVariableNum(newval, -1, &valid);
+	if (valid)
+		pset.fetch_count = value;
+	else
+	{
+		psql_error("invalid value \"%s\" for \"%s\"\n",
+				   newval, "FETCH_COUNT");
+		return false;
+	}
+	return true;
 }
 
-static void
+static bool
 echo_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -837,39 +862,52 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "ECHO", "none");
-		pset.echo = PSQL_ECHO_NONE;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "ECHO");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 echo_hidden_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
 	else if (pg_strcasecmp(newval, "noexec") == 0)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
-	else if (ParseVariableBool(newval, "ECHO_HIDDEN"))
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ECHO_HIDDEN", &isvalid);
+		if (!isvalid)
+			return false; /* ParseVariableBool printed msg */
+		pset.echo_hidden = val ? PSQL_ECHO_HIDDEN_ON : PSQL_ECHO_HIDDEN_OFF;
+	}
+	return true;
 }
 
-static void
+static bool
 on_error_rollback_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
 	else if (pg_strcasecmp(newval, "interactive") == 0)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
-	else if (ParseVariableBool(newval, "ON_ERROR_ROLLBACK"))
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, "ON_ERROR_ROLLBACK", &isvalid);
+		if (isvalid)
+			pset.on_error_rollback = val ? PSQL_ERROR_ROLLBACK_ON : PSQL_ERROR_ROLLBACK_OFF;
+		else
+			/* ParseVariableBool printed msg if needed */
+			return false;
+	}
+	return true;
 }
 
-static void
+static bool
 comp_keyword_case_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -884,13 +922,14 @@ comp_keyword_case_hook(const char *newval)
 		pset.comp_case = PSQL_COMP_CASE_LOWER;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "COMP_KEYWORD_CASE", "preserve-upper");
-		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "COMP_KEYWORD_CASE");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 histcontrol_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -905,31 +944,35 @@ histcontrol_hook(const char *newval)
 		pset.histcontrol = hctl_none;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "HISTCONTROL", "none");
-		pset.histcontrol = hctl_none;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "HISTCONTROL");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 prompt1_hook(const char *newval)
 {
 	pset.prompt1 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt2_hook(const char *newval)
 {
 	pset.prompt2 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt3_hook(const char *newval)
 {
 	pset.prompt3 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 verbosity_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -942,16 +985,17 @@ verbosity_hook(const char *newval)
 		pset.verbosity = PQERRORS_VERBOSE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "VERBOSITY", "default");
-		pset.verbosity = PQERRORS_DEFAULT;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "VERBOSITY");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorVerbosity(pset.db, pset.verbosity);
+	return true;
 }
 
-static void
+static bool
 show_context_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -964,13 +1008,14 @@ show_context_hook(const char *newval)
 		pset.show_context = PQSHOW_CONTEXT_ALWAYS;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "SHOW_CONTEXT", "errors");
-		pset.show_context = PQSHOW_CONTEXT_ERRORS;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "SHOW_CONTEXT");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorContextVisibility(pset.db, pset.show_context);
+	return true;
 }
 
 
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index f43f418..1302a32 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -86,24 +86,28 @@ GetVariable(VariableSpace space, const char *name)
  *
  * "name" is the name of the variable we're assigning to, to use in error
  * report if any.  Pass name == NULL to suppress the error report.
+ *
+ * "*valid" reports whether "value" was syntactically valid, unless valid == NULL
  */
 bool
-ParseVariableBool(const char *value, const char *name)
+ParseVariableBool(const char *value, const char *name, bool *valid)
 {
 	size_t		len;
 
+	if (valid)
+		*valid = true;
 	if (value == NULL)
 		return false;			/* not set -> assume "off" */
 
 	len = strlen(value);
 
-	if (pg_strncasecmp(value, "true", len) == 0)
+	if (len > 0 && pg_strncasecmp(value, "true", len) == 0)
 		return true;
-	else if (pg_strncasecmp(value, "false", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "false", len) == 0)
 		return false;
-	else if (pg_strncasecmp(value, "yes", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "yes", len) == 0)
 		return true;
-	else if (pg_strncasecmp(value, "no", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "no", len) == 0)
 		return false;
 	/* 'o' is not unique enough */
 	else if (pg_strncasecmp(value, "on", (len > 2 ? len : 2)) == 0)
@@ -116,10 +120,16 @@ ParseVariableBool(const char *value, const char *name)
 		return false;
 	else
 	{
-		/* NULL is treated as false, so a non-matching value is 'true' */
+		/*
+		 * NULL is treated as false, so a non-matching value is 'true'.
+		 * A caller that cares about syntactic conformance should
+		 * check *valid to know whether the value was recognized.
+		 */
 		if (name)
-			psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-					   value, name, "on");
+			psql_error("unrecognized value \"%s\" for \"%s\": boolean expected\n",
+					   value, name);
+		if (valid)
+			*valid = false;
 		return true;
 	}
 }
@@ -154,6 +164,35 @@ ParseVariableNum(const char *val,
 	return result;
 }
 
+/*
+ * Read numeric variable, or defaultval if it is not set.
+ * Trailing contents are not allowed.
+ * "valid" points to a bool reporting whether the value was valid.
+ */
+int
+ParseCheckVariableNum(const char *val,
+					  int defaultval,
+					  bool *valid)
+{
+	int		result;
+
+	if (!val)
+	{
+		*valid = true;
+		result = defaultval;
+	}
+	else
+	{
+		char	   *end;
+
+		errno = 0;
+		result = strtol(val, &end, 0);
+		*valid = (val[0] != '\0' && errno == 0 && *end == '\0');
+	}
+
+	return result;
+}
+
 int
 GetVariableNum(VariableSpace space,
 			   const char *name,
@@ -205,13 +244,26 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 	{
 		if (strcmp(current->name, name) == 0)
 		{
-			/* found entry, so update */
-			if (current->value)
-				free(current->value);
-			current->value = pg_strdup(value);
-			if (current->assign_hook)
-				(*current->assign_hook) (current->value);
-			return true;
+			/*
+			 * Found entry, so update, unless a hook returns false.
+			 * The hook needs the value in a buffer with the same lifespan
+			 * as the variable, so allocate it right away, even if it needs
+			 * to be freed just after when the hook returns false.
+			 */
+			char *new_value = pg_strdup(value);
+
+			bool confirmed = current->assign_hook ?
+							(*current->assign_hook) (new_value) : true;
+
+			if (confirmed)
+			{
+				pg_free(current->value);
+				current->value = new_value;
+			}
+			else
+				pg_free(new_value); /* and current->value is left unchanged */
+
+			return confirmed;
 		}
 	}
 
@@ -248,8 +300,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 		{
 			/* found entry, so update */
 			current->assign_hook = hook;
-			(*hook) (current->value);
-			return true;
+			return (*hook) (current->value);
 		}
 	}
 
@@ -260,8 +311,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(*hook) (NULL);
-	return true;
+	return (*hook) (NULL);
 }
 
 bool
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index d7a05a1..38396ba 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -20,7 +20,7 @@
  * Note: if value == NULL then the variable is logically unset, but we are
  * keeping the struct around so as not to forget about its hook function.
  */
-typedef void (*VariableAssignHook) (const char *newval);
+typedef bool (*VariableAssignHook) (const char *newval);
 
 struct _variable
 {
@@ -35,11 +35,14 @@ typedef struct _variable *VariableSpace;
 VariableSpace CreateVariableSpace(void);
 const char *GetVariable(VariableSpace space, const char *name);
 
-bool		ParseVariableBool(const char *value, const char *name);
+bool		ParseVariableBool(const char *value, const char *name, bool *valid);
 int ParseVariableNum(const char *val,
 				 int defaultval,
 				 int faultval,
 				 bool allowtrail);
+int ParseCheckVariableNum(const char *val,
+						  int defaultval,
+						  bool *valid);
 int GetVariableNum(VariableSpace space,
 			   const char *name,
 			   int defaultval,

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a9a2fdb..46bcf19 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -254,25 +254,30 @@ exec_command(const char *cmd,
 		if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
 		{
 			reuse_previous =
-				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
+				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix, &success) ?
 				TRI_YES : TRI_NO;
-
-			free(opt1);
-			opt1 = read_connect_arg(scan_state);
+			if (success)
+			{
+				free(opt1);
+				opt1 = read_connect_arg(scan_state);
+			}
 		}
 		else
 			reuse_previous = TRI_DEFAULT;
 
-		opt2 = read_connect_arg(scan_state);
-		opt3 = read_connect_arg(scan_state);
-		opt4 = read_connect_arg(scan_state);
+		if (success)			/* do not attempt to connect if reuse_previous argument was invalid */
+		{
+			opt2 = read_connect_arg(scan_state);
+			opt3 = read_connect_arg(scan_state);
+			opt4 = read_connect_arg(scan_state);
 
-		success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
+			success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
 
+			free(opt2);
+			free(opt3);
+			free(opt4);
+		}
 		free(opt1);
-		free(opt2);
-		free(opt3);
-		free(opt4);
 	}
 
 	/* \cd */
@@ -1548,7 +1553,11 @@ exec_command(const char *cmd,
 												 OT_NORMAL, NULL, false);
 
 		if (opt)
-			pset.timing = ParseVariableBool(opt, "\\timing");
+		{
+			bool	newval = ParseVariableBool(opt, "\\timing", &success);
+			if (success)
+				pset.timing = newval;
+		}
 		else
 			pset.timing = !pset.timing;
 		if (!pset.quiet)
@@ -2660,7 +2669,18 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		if (value && pg_strcasecmp(value, "auto") == 0)
 			popt->topt.expanded = 2;
 		else if (value)
-			popt->topt.expanded = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, NULL, &valid);
+			if (valid)
+				popt->topt.expanded = newval;
+			else
+			{
+				psql_error("unrecognized value \"%s\" for \"%s\"\n",
+						   value, param);
+				return false;
+			}
+		}
 		else
 			popt->topt.expanded = !popt->topt.expanded;
 	}
@@ -2669,7 +2689,14 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "numericlocale") == 0)
 	{
 		if (value)
-			popt->topt.numericLocale = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, param, &valid);
+			if (valid)
+				popt->topt.numericLocale = newval;
+			else
+				return false;
+		}
 		else
 			popt->topt.numericLocale = !popt->topt.numericLocale;
 	}
@@ -2724,7 +2751,18 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "t") == 0 || strcmp(param, "tuples_only") == 0)
 	{
 		if (value)
-			popt->topt.tuples_only = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, NULL, &valid);
+			if (valid)
+				popt->topt.tuples_only = newval;
+			else
+			{
+				psql_error("unrecognized value \"%s\" for \"%s\"\n",
+						   value, param);
+				return false;
+			}
+		}
 		else
 			popt->topt.tuples_only = !popt->topt.tuples_only;
 	}
@@ -2756,10 +2794,15 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 			popt->topt.pager = 2;
 		else if (value)
 		{
-			if (ParseVariableBool(value, param))
-				popt->topt.pager = 1;
-			else
-				popt->topt.pager = 0;
+			bool	valid;
+			bool	on = ParseVariableBool(value, NULL, &valid);
+			if (!valid)
+			{
+				psql_error("unrecognized value \"%s\" for \"%s\"\n",
+						   value, param);
+				return false;
+			}
+			popt->topt.pager = on ? 1 : 0;
 		}
 		else if (popt->topt.pager == 1)
 			popt->topt.pager = 0;
@@ -2778,7 +2821,14 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "footer") == 0)
 	{
 		if (value)
-			popt->topt.default_footer = ParseVariableBool(value, param);
+		{
+			bool	valid;
+			bool	newval = ParseVariableBool(value, param, &valid);
+			if (valid)
+				popt->topt.default_footer = newval;
+			else
+				return false;
+		}
 		else
 			popt->topt.default_footer = !popt->topt.default_footer;
 	}
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 7ce05fb..b8281d4 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -786,43 +786,68 @@ showVersion(void)
  * This isn't an amazingly good place for them, but neither is anywhere else.
  */
 
-static void
+/*
+ * Hook to set an internal flag from a user-supplied string value.
+ * If the syntax is correct, affect *flag and return true.
+ * Otherwise, keep *flag untouched and return false.
+ */
+static bool
+generic_boolean_hook(const char *newval, const char* varname, bool *flag)
+{
+	bool isvalid;
+	bool val = ParseVariableBool(newval, varname, &isvalid);
+	if (isvalid)
+		*flag = val;
+	return isvalid;
+}
+
+static bool
 autocommit_hook(const char *newval)
 {
-	pset.autocommit = ParseVariableBool(newval, "AUTOCOMMIT");
+	return generic_boolean_hook(newval, "AUTOCOMMIT", &pset.autocommit);
 }
 
-static void
+static bool
 on_error_stop_hook(const char *newval)
 {
-	pset.on_error_stop = ParseVariableBool(newval, "ON_ERROR_STOP");
+	return generic_boolean_hook(newval, "ON_ERROR_STOP", &pset.on_error_stop);
 }
 
-static void
+static bool
 quiet_hook(const char *newval)
 {
-	pset.quiet = ParseVariableBool(newval, "QUIET");
+	return generic_boolean_hook(newval, "QUIET", &pset.quiet);
 }
 
-static void
+static bool
 singleline_hook(const char *newval)
 {
-	pset.singleline = ParseVariableBool(newval, "SINGLELINE");
+	return generic_boolean_hook(newval, "SINGLELINE", &pset.singleline);
 }
 
-static void
+static bool
 singlestep_hook(const char *newval)
 {
-	pset.singlestep = ParseVariableBool(newval, "SINGLESTEP");
+	return generic_boolean_hook(newval, "SINGLESTEP", &pset.singlestep);
 }
 
-static void
+static bool
 fetch_count_hook(const char *newval)
 {
-	pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
+	bool valid;
+	int value = ParseCheckVariableNum(newval, -1, &valid);
+	if (valid)
+		pset.fetch_count = value;
+	else
+	{
+		psql_error("invalid value \"%s\" for \"%s\"\n",
+				   newval, "FETCH_COUNT");
+		return false;
+	}
+	return true;
 }
 
-static void
+static bool
 echo_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -837,39 +862,59 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "ECHO", "none");
-		pset.echo = PSQL_ECHO_NONE;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "ECHO");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 echo_hidden_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
 	else if (pg_strcasecmp(newval, "noexec") == 0)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
-	else if (ParseVariableBool(newval, "ECHO_HIDDEN"))
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, NULL, &isvalid);
+		if (!isvalid)
+		{
+			psql_error("unrecognized value \"%s\" for \"%s\"\n",
+					   newval, "ECHO_HIDDEN");
+			return false;
+		}
+		pset.echo_hidden = val ? PSQL_ECHO_HIDDEN_ON : PSQL_ECHO_HIDDEN_OFF;
+	}
+	return true;
 }
 
-static void
+static bool
 on_error_rollback_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
 	else if (pg_strcasecmp(newval, "interactive") == 0)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
-	else if (ParseVariableBool(newval, "ON_ERROR_ROLLBACK"))
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
+	else
+	{
+		bool isvalid;
+		bool val = ParseVariableBool(newval, NULL, &isvalid);
+		if (isvalid)
+			pset.on_error_rollback = val ? PSQL_ERROR_ROLLBACK_ON : PSQL_ERROR_ROLLBACK_OFF;
+		else
+		{
+			psql_error("unrecognized value \"%s\" for \"%s\"\n",
+					   newval, "ON_ERROR_ROLLBACK");
+			return false;
+		}
+	}
+	return true;
 }
 
-static void
+static bool
 comp_keyword_case_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -884,13 +929,14 @@ comp_keyword_case_hook(const char *newval)
 		pset.comp_case = PSQL_COMP_CASE_LOWER;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "COMP_KEYWORD_CASE", "preserve-upper");
-		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "COMP_KEYWORD_CASE");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 histcontrol_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -905,31 +951,35 @@ histcontrol_hook(const char *newval)
 		pset.histcontrol = hctl_none;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "HISTCONTROL", "none");
-		pset.histcontrol = hctl_none;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "HISTCONTROL");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 prompt1_hook(const char *newval)
 {
 	pset.prompt1 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt2_hook(const char *newval)
 {
 	pset.prompt2 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt3_hook(const char *newval)
 {
 	pset.prompt3 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 verbosity_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -942,16 +992,17 @@ verbosity_hook(const char *newval)
 		pset.verbosity = PQERRORS_VERBOSE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "VERBOSITY", "default");
-		pset.verbosity = PQERRORS_DEFAULT;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "VERBOSITY");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorVerbosity(pset.db, pset.verbosity);
+	return true;
 }
 
-static void
+static bool
 show_context_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -964,13 +1015,14 @@ show_context_hook(const char *newval)
 		pset.show_context = PQSHOW_CONTEXT_ALWAYS;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "SHOW_CONTEXT", "errors");
-		pset.show_context = PQSHOW_CONTEXT_ERRORS;
+		psql_error("unrecognized value \"%s\" for \"%s\"\n",
+				   newval, "SHOW_CONTEXT");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorContextVisibility(pset.db, pset.show_context);
+	return true;
 }
 
 
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index f43f418..453ef46 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -86,24 +86,27 @@ GetVariable(VariableSpace space, const char *name)
  *
  * "name" is the name of the variable we're assigning to, to use in error
  * report if any.  Pass name == NULL to suppress the error report.
+ *
+ * "*valid" reports whether "value" was syntactically valid
  */
 bool
-ParseVariableBool(const char *value, const char *name)
+ParseVariableBool(const char *value, const char *name, bool *valid)
 {
 	size_t		len;
 
+	*valid = true;
 	if (value == NULL)
 		return false;			/* not set -> assume "off" */
 
 	len = strlen(value);
 
-	if (pg_strncasecmp(value, "true", len) == 0)
+	if (len > 0 && pg_strncasecmp(value, "true", len) == 0)
 		return true;
-	else if (pg_strncasecmp(value, "false", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "false", len) == 0)
 		return false;
-	else if (pg_strncasecmp(value, "yes", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "yes", len) == 0)
 		return true;
-	else if (pg_strncasecmp(value, "no", len) == 0)
+	else if (len > 0 && pg_strncasecmp(value, "no", len) == 0)
 		return false;
 	/* 'o' is not unique enough */
 	else if (pg_strncasecmp(value, "on", (len > 2 ? len : 2)) == 0)
@@ -116,10 +119,15 @@ ParseVariableBool(const char *value, const char *name)
 		return false;
 	else
 	{
-		/* NULL is treated as false, so a non-matching value is 'true' */
+		/*
+		 * NULL is treated as false, so a non-matching value is 'true'.
+		 * A caller that cares about syntactic conformance should
+		 * check *valid to know whether the value was recognized.
+		 */
 		if (name)
-			psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-					   value, name, "on");
+			psql_error("unrecognized value \"%s\" for \"%s\": boolean expected\n",
+					   value, name);
+		*valid = false;
 		return true;
 	}
 }
@@ -154,6 +162,35 @@ ParseVariableNum(const char *val,
 	return result;
 }
 
+/*
+ * Read numeric variable, or defaultval if it is not set.
+ * Trailing contents are not allowed.
+ * "valid" points to a bool reporting whether the value was valid.
+ */
+int
+ParseCheckVariableNum(const char *val,
+					  int defaultval,
+					  bool *valid)
+{
+	int		result;
+
+	if (!val)
+	{
+		*valid = true;
+		result = defaultval;
+	}
+	else
+	{
+		char	   *end;
+
+		errno = 0;
+		result = strtol(val, &end, 0);
+		*valid = (val[0] != '\0' && errno == 0 && *end == '\0');
+	}
+
+	return result;
+}
+
 int
 GetVariableNum(VariableSpace space,
 			   const char *name,
@@ -205,13 +242,26 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 	{
 		if (strcmp(current->name, name) == 0)
 		{
-			/* found entry, so update */
-			if (current->value)
-				free(current->value);
-			current->value = pg_strdup(value);
-			if (current->assign_hook)
-				(*current->assign_hook) (current->value);
-			return true;
+			/*
+			 * Found entry, so update, unless a hook returns false.
+			 * The hook needs the value in a buffer with the same lifespan
+			 * as the variable, so allocate it right away, even if it needs
+			 * to be freed just after when the hook returns false.
+			 */
+			char *new_value = pg_strdup(value);
+
+			bool confirmed = current->assign_hook ?
+							(*current->assign_hook) (new_value) : true;
+
+			if (confirmed)
+			{
+				pg_free(current->value);
+				current->value = new_value;
+			}
+			else
+				pg_free(new_value); /* and current->value is left unchanged */
+
+			return confirmed;
 		}
 	}
 
@@ -248,8 +298,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 		{
 			/* found entry, so update */
 			current->assign_hook = hook;
-			(*hook) (current->value);
-			return true;
+			return (*hook) (current->value);
 		}
 	}
 
@@ -260,8 +309,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(*hook) (NULL);
-	return true;
+	return (*hook) (NULL);
 }
 
 bool
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index d7a05a1..38396ba 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -20,7 +20,7 @@
  * Note: if value == NULL then the variable is logically unset, but we are
  * keeping the struct around so as not to forget about its hook function.
  */
-typedef void (*VariableAssignHook) (const char *newval);
+typedef bool (*VariableAssignHook) (const char *newval);
 
 struct _variable
 {
@@ -35,11 +35,14 @@ typedef struct _variable *VariableSpace;
 VariableSpace CreateVariableSpace(void);
 const char *GetVariable(VariableSpace space, const char *name);
 
-bool		ParseVariableBool(const char *value, const char *name);
+bool		ParseVariableBool(const char *value, const char *name, bool *valid);
 int ParseVariableNum(const char *val,
 				 int defaultval,
 				 int faultval,
 				 bool allowtrail);
+int ParseCheckVariableNum(const char *val,
+						  int defaultval,
+						  bool *valid);
 int GetVariableNum(VariableSpace space,
 			   const char *name,
 			   int defaultval,

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 9915731..042d277 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -3213,9 +3213,8 @@ bar
          list. If set to a value of <literal>ignoredups</literal>, lines
          matching the previous history line are not entered. A value of
          <literal>ignoreboth</literal> combines the two options. If
-         unset, or if set to <literal>none</literal> (or any other value
-         than those above), all lines read in interactive mode are
-         saved on the history list.
+         unset, or if set to <literal>none</literal>, all lines read
+         in interactive mode are saved on the history list.
         </para>
         <note>
         <para>
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 4139b77..091a138 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -253,26 +253,31 @@ exec_command(const char *cmd,
 		opt1 = read_connect_arg(scan_state);
 		if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
 		{
-			reuse_previous =
-				ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
-				TRI_YES : TRI_NO;
-
-			free(opt1);
-			opt1 = read_connect_arg(scan_state);
+			bool on_off;
+			success = ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix, &on_off);
+			if (success)
+			{
+				reuse_previous = on_off ? TRI_YES : TRI_NO;
+				free(opt1);
+				opt1 = read_connect_arg(scan_state);
+			}
 		}
 		else
 			reuse_previous = TRI_DEFAULT;
 
-		opt2 = read_connect_arg(scan_state);
-		opt3 = read_connect_arg(scan_state);
-		opt4 = read_connect_arg(scan_state);
+		if (success)			/* do not attempt to connect if reuse_previous argument was invalid */
+		{
+			opt2 = read_connect_arg(scan_state);
+			opt3 = read_connect_arg(scan_state);
+			opt4 = read_connect_arg(scan_state);
 
-		success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
+			success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
 
+			free(opt2);
+			free(opt3);
+			free(opt4);
+		}
 		free(opt1);
-		free(opt2);
-		free(opt3);
-		free(opt4);
 	}
 
 	/* \cd */
@@ -1548,7 +1553,7 @@ exec_command(const char *cmd,
 												 OT_NORMAL, NULL, false);
 
 		if (opt)
-			pset.timing = ParseVariableBool(opt, "\\timing");
+			success = ParseVariableBool(opt, "\\timing", &pset.timing);
 		else
 			pset.timing = !pset.timing;
 		if (!pset.quiet)
@@ -2660,7 +2665,16 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		if (value && pg_strcasecmp(value, "auto") == 0)
 			popt->topt.expanded = 2;
 		else if (value)
-			popt->topt.expanded = ParseVariableBool(value, param);
+		{
+			bool on_off;
+			if (ParseVariableBool(value, NULL, &on_off))
+				popt->topt.expanded = on_off ? 1 : 0;
+			else
+			{
+				PsqlVarEnumError(param, value, "on, off, auto");
+				return false;
+			}
+		}
 		else
 			popt->topt.expanded = !popt->topt.expanded;
 	}
@@ -2669,7 +2683,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "numericlocale") == 0)
 	{
 		if (value)
-			popt->topt.numericLocale = ParseVariableBool(value, param);
+			return ParseVariableBool(value, param, &popt->topt.numericLocale);
 		else
 			popt->topt.numericLocale = !popt->topt.numericLocale;
 	}
@@ -2724,7 +2738,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "t") == 0 || strcmp(param, "tuples_only") == 0)
 	{
 		if (value)
-			popt->topt.tuples_only = ParseVariableBool(value, param);
+			return ParseVariableBool(value, param, &popt->topt.tuples_only);
 		else
 			popt->topt.tuples_only = !popt->topt.tuples_only;
 	}
@@ -2756,10 +2770,13 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 			popt->topt.pager = 2;
 		else if (value)
 		{
-			if (ParseVariableBool(value, param))
-				popt->topt.pager = 1;
-			else
-				popt->topt.pager = 0;
+			bool on_off;
+			if (!ParseVariableBool(value, NULL, &on_off))
+			{
+				PsqlVarEnumError(param, value, "on, off, always");
+				return false;
+			}
+			popt->topt.pager = on_off ? 1 : 0;
 		}
 		else if (popt->topt.pager == 1)
 			popt->topt.pager = 0;
@@ -2778,7 +2795,7 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 	else if (strcmp(param, "footer") == 0)
 	{
 		if (value)
-			popt->topt.default_footer = ParseVariableBool(value, param);
+			return ParseVariableBool(value, param, &popt->topt.default_footer);
 		else
 			popt->topt.default_footer = !popt->topt.default_footer;
 	}
diff --git a/src/bin/psql/input.c b/src/bin/psql/input.c
index 972bea4..3e3e97a 100644
--- a/src/bin/psql/input.c
+++ b/src/bin/psql/input.c
@@ -541,7 +541,7 @@ finishInput(void)
 	{
 		int			hist_size;
 
-		hist_size = GetVariableNum(pset.vars, "HISTSIZE", 500, -1, true);
+		hist_size = GetVariableNum(pset.vars, "HISTSIZE", 500, -1);
 		(void) saveHistory(psql_history, hist_size);
 		free(psql_history);
 		psql_history = NULL;
diff --git a/src/bin/psql/mainloop.c b/src/bin/psql/mainloop.c
index bb306a4..dc25b4b 100644
--- a/src/bin/psql/mainloop.c
+++ b/src/bin/psql/mainloop.c
@@ -162,7 +162,7 @@ MainLoop(FILE *source)
 				/* This tries to mimic bash's IGNOREEOF feature. */
 				count_eof++;
 
-				if (count_eof < GetVariableNum(pset.vars, "IGNOREEOF", 0, 10, false))
+				if (count_eof < GetVariableNum(pset.vars, "IGNOREEOF", 0, 10))
 				{
 					if (!pset.quiet)
 						printf(_("Use \"\\q\" to leave %s.\n"), pset.progname);
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 85aac4a..0b4f43e 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -786,43 +786,71 @@ showVersion(void)
  * This isn't an amazingly good place for them, but neither is anywhere else.
  */
 
-static void
+
+static bool
 autocommit_hook(const char *newval)
 {
-	pset.autocommit = ParseVariableBool(newval, "AUTOCOMMIT");
+	bool autocommit;
+	if (ParseVariableBool(newval, "AUTOCOMMIT", &autocommit))
+	{
+		/*
+		 * Switching AUTOCOMMIT from OFF to ON is not allowed when inside a
+		 * transaction, because it cannot be effective until the current
+		 * transaction is ended.
+		 */
+		if (autocommit && !pset.autocommit &&
+			pset.db && PQtransactionStatus(pset.db) == PQTRANS_INTRANS)
+		{
+			psql_error("cannot set AUTOCOMMIT to %s when inside a transaction\n", newval);
+		}
+		else
+		{
+			pset.autocommit = autocommit;
+			return true;
+		}
+	}
+	return false;
 }
 
-static void
+static bool
 on_error_stop_hook(const char *newval)
 {
-	pset.on_error_stop = ParseVariableBool(newval, "ON_ERROR_STOP");
+	return ParseVariableBool(newval, "ON_ERROR_STOP", &pset.on_error_stop);
 }
 
-static void
+static bool
 quiet_hook(const char *newval)
 {
-	pset.quiet = ParseVariableBool(newval, "QUIET");
+	return ParseVariableBool(newval, "QUIET", &pset.quiet);
 }
 
-static void
+static bool
 singleline_hook(const char *newval)
 {
-	pset.singleline = ParseVariableBool(newval, "SINGLELINE");
+	return ParseVariableBool(newval, "SINGLELINE", &pset.singleline);
 }
 
-static void
+static bool
 singlestep_hook(const char *newval)
 {
-	pset.singlestep = ParseVariableBool(newval, "SINGLESTEP");
+	return ParseVariableBool(newval, "SINGLESTEP", &pset.singlestep);
 }
 
-static void
+static bool
 fetch_count_hook(const char *newval)
 {
-	pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
+	if (newval == NULL)
+		pset.fetch_count = -1;	/* default value */
+	else if (!ParseVariableNum(newval, &pset.fetch_count))
+	{
+		psql_error("Invalid value \"%s\" for \"%s\"\nAn integer is expected\n",
+				   newval, "FETCH_COUNT");
+		return false;
+	}
+	return true;
 }
 
-static void
+static bool
 echo_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -837,39 +865,55 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "ECHO", "none");
-		pset.echo = PSQL_ECHO_NONE;
+		PsqlVarEnumError("ECHO", newval, "none, errors, queries, all");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 echo_hidden_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
 	else if (pg_strcasecmp(newval, "noexec") == 0)
 		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
-	else if (ParseVariableBool(newval, "ECHO_HIDDEN"))
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
+	else
+	{
+		bool on_off;
+		if (ParseVariableBool(newval, NULL, &on_off))
+			pset.echo_hidden = on_off ? PSQL_ECHO_HIDDEN_ON : PSQL_ECHO_HIDDEN_OFF;
+		else
+		{
+			PsqlVarEnumError("ECHO_HIDDEN", newval, "on, off, noexec");
+			return false;
+		}
+	}
+	return true;
 }
 
-static void
+static bool
 on_error_rollback_hook(const char *newval)
 {
 	if (newval == NULL)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
 	else if (pg_strcasecmp(newval, "interactive") == 0)
 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
-	else if (ParseVariableBool(newval, "ON_ERROR_ROLLBACK"))
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_ON;
-	else	/* ParseVariableBool printed msg if needed */
-		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
+	else
+	{
+		bool on_off;
+		if (ParseVariableBool(newval, NULL, &on_off))
+			pset.on_error_rollback = on_off ? PSQL_ERROR_ROLLBACK_ON : PSQL_ERROR_ROLLBACK_OFF;
+		else
+		{
+			PsqlVarEnumError("ON_ERROR_ROLLBACK", newval, "on, off, interactive");
+			return false;
+		}
+	}
+	return true;
 }
 
-static void
+static bool
 comp_keyword_case_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -884,13 +928,14 @@ comp_keyword_case_hook(const char *newval)
 		pset.comp_case = PSQL_COMP_CASE_LOWER;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "COMP_KEYWORD_CASE", "preserve-upper");
-		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
+		PsqlVarEnumError("COMP_KEYWORD_CASE", newval,
+						 "lower, upper, preserve-lower, preserve-upper");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 histcontrol_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -905,31 +950,35 @@ histcontrol_hook(const char *newval)
 		pset.histcontrol = hctl_none;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "HISTCONTROL", "none");
-		pset.histcontrol = hctl_none;
+		PsqlVarEnumError("HISTCONTROL", newval,
+						 "none, ignorespace, ignoredups, ignoreboth");
+		return false;
 	}
+	return true;
 }
 
-static void
+static bool
 prompt1_hook(const char *newval)
 {
 	pset.prompt1 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt2_hook(const char *newval)
 {
 	pset.prompt2 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 prompt3_hook(const char *newval)
 {
 	pset.prompt3 = newval ? newval : "";
+	return true;
 }
 
-static void
+static bool
 verbosity_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -942,16 +991,16 @@ verbosity_hook(const char *newval)
 		pset.verbosity = PQERRORS_VERBOSE;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "VERBOSITY", "default");
-		pset.verbosity = PQERRORS_DEFAULT;
+		PsqlVarEnumError("VERBOSITY", newval, "default, terse, verbose");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorVerbosity(pset.db, pset.verbosity);
+	return true;
 }
 
-static void
+static bool
 show_context_hook(const char *newval)
 {
 	if (newval == NULL)
@@ -964,13 +1013,13 @@ show_context_hook(const char *newval)
 		pset.show_context = PQSHOW_CONTEXT_ALWAYS;
 	else
 	{
-		psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-				   newval, "SHOW_CONTEXT", "errors");
-		pset.show_context = PQSHOW_CONTEXT_ERRORS;
+		PsqlVarEnumError("SHOW_CONTEXT", newval, "never, errors, always");
+		return false;
 	}
 
 	if (pset.db)
 		PQsetErrorContextVisibility(pset.db, pset.show_context);
+	return true;
 }
 
 
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index 2669572..d0de198 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -79,92 +79,103 @@ GetVariable(VariableSpace space, const char *name)
 }
 
 /*
- * Try to interpret "value" as boolean value.
+ * Try to interpret "value" as boolean value, and if successful,
+ * put it in *result. Otherwise don't clobber *result.
  *
  * Valid values are: true, false, yes, no, on, off, 1, 0; as well as unique
  * prefixes thereof.
  *
  * "name" is the name of the variable we're assigning to, to use in error
  * report if any.  Pass name == NULL to suppress the error report.
+ *
+ * Return true when "value" is syntactically valid, false otherwise.
  */
 bool
-ParseVariableBool(const char *value, const char *name)
+ParseVariableBool(const char *value, const char *name, bool *result)
 {
 	size_t		len;
+	bool		valid = true;
 
 	if (value == NULL)
-		return false;			/* not set -> assume "off" */
+	{
+		*result = false;			/* not set -> assume "off" */
+		return valid;
+	}
 
 	len = strlen(value);
 
-	if (pg_strncasecmp(value, "true", len) == 0)
-		return true;
-	else if (pg_strncasecmp(value, "false", len) == 0)
-		return false;
-	else if (pg_strncasecmp(value, "yes", len) == 0)
-		return true;
-	else if (pg_strncasecmp(value, "no", len) == 0)
-		return false;
+	if (len > 0 && pg_strncasecmp(value, "true", len) == 0)
+		*result = true;
+	else if (len > 0 && pg_strncasecmp(value, "false", len) == 0)
+		*result = false;
+	else if (len > 0 && pg_strncasecmp(value, "yes", len) == 0)
+		*result = true;
+	else if (len > 0 && pg_strncasecmp(value, "no", len) == 0)
+		*result = false;
 	/* 'o' is not unique enough */
 	else if (pg_strncasecmp(value, "on", (len > 2 ? len : 2)) == 0)
-		return true;
+		*result = true;
 	else if (pg_strncasecmp(value, "off", (len > 2 ? len : 2)) == 0)
-		return false;
+		*result = false;
 	else if (pg_strcasecmp(value, "1") == 0)
-		return true;
+		*result = true;
 	else if (pg_strcasecmp(value, "0") == 0)
-		return false;
+		*result = false;
 	else
 	{
-		/* NULL is treated as false, so a non-matching value is 'true' */
+		/*
+		 * The string is not recognized. We don't clobber *result in this case.
+		 */
 		if (name)
-			psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
-					   value, name, "on");
-		return true;
+			psql_error("unrecognized value \"%s\" for \"%s\": boolean expected\n",
+					   value, name);
+		valid = false;
 	}
+	return valid;
 }
 
 
 /*
- * Read numeric variable, or defaultval if it is not set, or faultval if its
- * value is not a valid numeric string.  If allowtrail is false, this will
- * include the case where there are trailing characters after the number.
+ * Parse a numeric variable from its string representation.
+ * If the syntax is valid, return true and set *result to the value.
+ * Otherwise return false and leave *result unchanged.
  */
-int
-ParseVariableNum(const char *val,
-				 int defaultval,
-				 int faultval,
-				 bool allowtrail)
+bool
+ParseVariableNum(const char *val, int *result)
 {
-	int			result;
+	char	*end;
+	int		numval;
 
-	if (!val)
-		result = defaultval;
-	else if (!val[0])
-		result = faultval;
-	else
+	if (!val || !val[0])
+		return false;
+	errno = 0;
+	numval = strtol(val, &end, 0);
+	if (errno == 0 && *end == '\0')
 	{
-		char	   *end;
-
-		result = strtol(val, &end, 0);
-		if (!allowtrail && *end)
-			result = faultval;
+		*result = numval;
+		return true;
 	}
-
-	return result;
+	return false;
 }
 
+
 int
 GetVariableNum(VariableSpace space,
 			   const char *name,
 			   int defaultval,
-			   int faultval,
-			   bool allowtrail)
+			   int faultval)
 {
 	const char *val;
+	int result;
 
 	val = GetVariable(space, name);
-	return ParseVariableNum(val, defaultval, faultval, allowtrail);
+	if (!val)
+		return defaultval;
+
+	if (ParseVariableNum(val, &result))
+		return result;
+	else
+		return faultval;
 }
 
 void
@@ -205,13 +216,26 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 	{
 		if (strcmp(current->name, name) == 0)
 		{
-			/* found entry, so update */
-			if (current->value)
-				free(current->value);
-			current->value = pg_strdup(value);
-			if (current->assign_hook)
-				(*current->assign_hook) (current->value);
-			return true;
+			/*
+			 * Found entry, so update, unless a hook returns false.
+			 * The hook needs the value in a buffer with the same lifespan
+			 * as the variable, so allocate it right away, even if it needs
+			 * to be freed just after when the hook returns false.
+			 */
+			char *new_value = pg_strdup(value);
+
+			bool confirmed = current->assign_hook ?
+							(*current->assign_hook) (new_value) : true;
+
+			if (confirmed)
+			{
+				pg_free(current->value);
+				current->value = new_value;
+			}
+			else
+				pg_free(new_value); /* and current->value is left unchanged */
+
+			return confirmed;
 		}
 	}
 
@@ -248,8 +272,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 		{
 			/* found entry, so update */
 			current->assign_hook = hook;
-			(*hook) (current->value);
-			return true;
+			return (*hook) (current->value);
 		}
 	}
 
@@ -260,8 +283,7 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(*hook) (NULL);
-	return true;
+	return (*hook) (NULL);
 }
 
 bool
@@ -303,3 +325,14 @@ DeleteVariable(VariableSpace space, const char *name)
 
 	return true;
 }
+
+/*
+ * Emit error with suggestions for variables or commands
+ * accepting enum-style arguments.
+ */
+void
+PsqlVarEnumError(const char* name, const char* value, const char* suggestions)
+{
+	psql_error("Unrecognized value \"%s\" for \"%s\"\nAvailable values: %s\n",
+			   value, name, suggestions);
+}
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index d235b17..c7d99d1 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -12,15 +12,19 @@
  * This implements a sort of variable repository. One could also think of it
  * as a cheap version of an associative array. In each one of these
  * datastructures you can store name/value pairs.  There can also be an
- * "assign hook" function that is called whenever the variable's value is
- * changed.
+ * "assign hook" function that is called before the variable's value is
+ * changed, and that returns a boolean indicating whether the assignment
+ * is confirmed or must be cancelled.
  *
- * An "unset" operation causes the hook to be called with newval == NULL.
+ * The hook is called with newval == NULL when a variable is created
+ * along with it by SetVariableAssignHook().
+ * An "unset" operation also causes the  hook to be called with newval == NULL,
+ * and is not cancellable even if the hook returns false.
  *
  * Note: if value == NULL then the variable is logically unset, but we are
  * keeping the struct around so as not to forget about its hook function.
  */
-typedef void (*VariableAssignHook) (const char *newval);
+typedef bool (*VariableAssignHook) (const char *newval);
 
 struct _variable
 {
@@ -35,16 +39,15 @@ typedef struct _variable *VariableSpace;
 VariableSpace CreateVariableSpace(void);
 const char *GetVariable(VariableSpace space, const char *name);
 
-bool		ParseVariableBool(const char *value, const char *name);
-int ParseVariableNum(const char *val,
-				 int defaultval,
-				 int faultval,
-				 bool allowtrail);
+bool		ParseVariableBool(const char *value, const char *name, bool *result);
+
+bool		ParseVariableNum(const char *val, int* result);
+
 int GetVariableNum(VariableSpace space,
 			   const char *name,
 			   int defaultval,
-			   int faultval,
-			   bool allowtrail);
+			   int faultval);
+
 
 void		PrintVariables(VariableSpace space);
 
@@ -53,4 +56,6 @@ bool		SetVariableAssignHook(VariableSpace space, const char *name, VariableAssig
 bool		SetVariableBool(VariableSpace space, const char *name);
 bool		DeleteVariable(VariableSpace space, const char *name);
 
+void		PsqlVarEnumError(const char* name, const char* value, const char* suggestions);
+
 #endif   /* VARIABLES_H */

diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 0574b5b..985cfcb 100644
*** a/src/bin/psql/startup.c
--- b/src/bin/psql/startup.c
*************** showVersion(void)
*** 777,787 ****
  
  
  /*
!  * Assign hooks for psql variables.
   *
   * This isn't an amazingly good place for them, but neither is anywhere else.
   */
  
  static bool
  autocommit_hook(const char *newval)
  {
--- 777,804 ----
  
  
  /*
!  * Substitute hooks and assign hooks for psql variables.
   *
   * This isn't an amazingly good place for them, but neither is anywhere else.
   */
  
+ static char *
+ bool_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 	{
+ 		/* "\unset FOO" becomes "\set FOO off" */
+ 		newval = pg_strdup("off");
+ 	}
+ 	else if (newval[0] == '\0')
+ 	{
+ 		/* "\set FOO" becomes "\set FOO on" */
+ 		pg_free(newval);
+ 		newval = pg_strdup("on");
+ 	}
+ 	return newval;
+ }
+ 
  static bool
  autocommit_hook(const char *newval)
  {
*************** EstablishVariableSpace(void)
*** 1002,1015 ****
--- 1019,1039 ----
  {
  	pset.vars = CreateVariableSpace();
  
+ 	SetVariableSubstituteHook(pset.vars, "AUTOCOMMIT", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "AUTOCOMMIT", autocommit_hook);
+ 	SetVariableSubstituteHook(pset.vars, "ON_ERROR_STOP", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "ON_ERROR_STOP", on_error_stop_hook);
+ 	SetVariableSubstituteHook(pset.vars, "QUIET", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "QUIET", quiet_hook);
+ 	SetVariableSubstituteHook(pset.vars, "SINGLELINE", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "SINGLELINE", singleline_hook);
+ 	SetVariableSubstituteHook(pset.vars, "SINGLESTEP", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "SINGLESTEP", singlestep_hook);
  	SetVariableAssignHook(pset.vars, "FETCH_COUNT", fetch_count_hook);
  	SetVariableAssignHook(pset.vars, "ECHO", echo_hook);
+ 	SetVariableSubstituteHook(pset.vars, "ECHO_HIDDEN", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "ECHO_HIDDEN", echo_hidden_hook);
+ 	SetVariableSubstituteHook(pset.vars, "ON_ERROR_ROLLBACK", bool_substitute_hook);
  	SetVariableAssignHook(pset.vars, "ON_ERROR_ROLLBACK", on_error_rollback_hook);
  	SetVariableAssignHook(pset.vars, "COMP_KEYWORD_CASE", comp_keyword_case_hook);
  	SetVariableAssignHook(pset.vars, "HISTCONTROL", histcontrol_hook);
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index 91e4ae8..61c4ccc 100644
*** a/src/bin/psql/variables.c
--- b/src/bin/psql/variables.c
*************** CreateVariableSpace(void)
*** 52,57 ****
--- 52,58 ----
  	ptr = pg_malloc(sizeof *ptr);
  	ptr->name = NULL;
  	ptr->value = NULL;
+ 	ptr->substitute_hook = NULL;
  	ptr->assign_hook = NULL;
  	ptr->next = NULL;
  
*************** ParseVariableBool(const char *value, con
*** 101,111 ****
  	size_t		len;
  	bool		valid = true;
  
  	if (value == NULL)
! 	{
! 		*result = false;		/* not set -> assume "off" */
! 		return valid;
! 	}
  
  	len = strlen(value);
  
--- 102,110 ----
  	size_t		len;
  	bool		valid = true;
  
+ 	/* Treat "unset" as an empty string, which will lead to error below */
  	if (value == NULL)
! 		value = "";
  
  	len = strlen(value);
  
*************** ParseVariableNum(const char *value, cons
*** 152,159 ****
  	char	   *end;
  	long		numval;
  
  	if (value == NULL)
! 		return false;
  	errno = 0;
  	numval = strtol(value, &end, 0);
  	if (errno == 0 && *end == '\0' && end != value && numval == (int) numval)
--- 151,160 ----
  	char	   *end;
  	long		numval;
  
+ 	/* Treat "unset" as an empty string, which will lead to error below */
  	if (value == NULL)
! 		value = "";
! 
  	errno = 0;
  	numval = strtol(value, &end, 0);
  	if (errno == 0 && *end == '\0' && end != value && numval == (int) numval)
*************** SetVariable(VariableSpace space, const c
*** 235,247 ****
  
  	if (!valid_variable_name(name))
  	{
  		psql_error("invalid variable name: \"%s\"\n", name);
  		return false;
  	}
  
- 	if (!value)
- 		return DeleteVariable(space, name);
- 
  	for (previous = space, current = space->next;
  		 current;
  		 previous = current, current = current->next)
--- 236,248 ----
  
  	if (!valid_variable_name(name))
  	{
+ 		/* Deletion of non-existent variable is not an error */
+ 		if (!value)
+ 			return true;
  		psql_error("invalid variable name: \"%s\"\n", name);
  		return false;
  	}
  
  	for (previous = space, current = space->next;
  		 current;
  		 previous = current, current = current->next)
*************** SetVariable(VariableSpace space, const c
*** 249,262 ****
  		if (strcmp(current->name, name) == 0)
  		{
  			/*
! 			 * Found entry, so update, unless hook returns false.  The hook
! 			 * may need the passed value to have the same lifespan as the
! 			 * variable, so allocate it right away, even though we'll have to
! 			 * free it again if the hook returns false.
  			 */
! 			char	   *new_value = pg_strdup(value);
  			bool		confirmed;
  
  			if (current->assign_hook)
  				confirmed = (*current->assign_hook) (new_value);
  			else
--- 250,269 ----
  		if (strcmp(current->name, name) == 0)
  		{
  			/*
! 			 * Found entry, so update, unless assign hook returns false.
! 			 *
! 			 * We must duplicate the passed value to start with.  This
! 			 * simplifies the API for substitute hooks.  Moreover, some assign
! 			 * hooks assume that the passed value has the same lifespan as the
! 			 * variable.  Having to free the string again on failure is a
! 			 * small price to pay for keeping these APIs simple.
  			 */
! 			char	   *new_value = value ? pg_strdup(value) : NULL;
  			bool		confirmed;
  
+ 			if (current->substitute_hook)
+ 				new_value = (*current->substitute_hook) (new_value);
+ 
  			if (current->assign_hook)
  				confirmed = (*current->assign_hook) (new_value);
  			else
*************** SetVariable(VariableSpace space, const c
*** 267,288 ****
  				if (current->value)
  					pg_free(current->value);
  				current->value = new_value;
  			}
! 			else
  				pg_free(new_value);		/* current->value is left unchanged */
  
  			return confirmed;
  		}
  	}
  
  	/* not present, make new entry */
  	current = pg_malloc(sizeof *current);
  	current->name = pg_strdup(name);
! 	current->value = pg_strdup(value);
  	current->assign_hook = NULL;
  	current->next = NULL;
  	previous->next = current;
! 	return true;
  }
  
  /*
--- 274,358 ----
  				if (current->value)
  					pg_free(current->value);
  				current->value = new_value;
+ 
+ 				/*
+ 				 * If we deleted the value, and there are no hooks to
+ 				 * remember, we can discard the variable altogether.
+ 				 */
+ 				if (new_value == NULL &&
+ 					current->substitute_hook == NULL &&
+ 					current->assign_hook == NULL)
+ 				{
+ 					previous->next = current->next;
+ 					free(current->name);
+ 					free(current);
+ 				}
  			}
! 			else if (new_value)
  				pg_free(new_value);		/* current->value is left unchanged */
  
  			return confirmed;
  		}
  	}
  
+ 	/* not present, make new entry ... unless we were asked to delete */
+ 	if (value)
+ 	{
+ 		current = pg_malloc(sizeof *current);
+ 		current->name = pg_strdup(name);
+ 		current->value = pg_strdup(value);
+ 		current->substitute_hook = NULL;
+ 		current->assign_hook = NULL;
+ 		current->next = NULL;
+ 		previous->next = current;
+ 	}
+ 	return true;
+ }
+ 
+ /*
+  * Attach a substitute hook function to the named variable.
+  *
+  * If the variable doesn't already exist, create it with value NULL,
+  * just so we have a place to store the hook function.  (But the hook
+  * might immediately change the NULL to something else.)
+  *
+  * The hook is immediately called on the variable's current value.
+  */
+ void
+ SetVariableSubstituteHook(VariableSpace space, const char *name,
+ 						  VariableSubstituteHook hook)
+ {
+ 	struct _variable *current,
+ 			   *previous;
+ 
+ 	if (!space || !name)
+ 		return;
+ 
+ 	if (!valid_variable_name(name))
+ 		return;
+ 
+ 	for (previous = space, current = space->next;
+ 		 current;
+ 		 previous = current, current = current->next)
+ 	{
+ 		if (strcmp(current->name, name) == 0)
+ 		{
+ 			/* found entry, so update */
+ 			current->substitute_hook = hook;
+ 			current->value = (*hook) (current->value);
+ 			return;
+ 		}
+ 	}
+ 
  	/* not present, make new entry */
  	current = pg_malloc(sizeof *current);
  	current->name = pg_strdup(name);
! 	current->value = NULL;
! 	current->substitute_hook = hook;
  	current->assign_hook = NULL;
  	current->next = NULL;
  	previous->next = current;
! 	current->value = (*hook) (current->value);
  }
  
  /*
*************** SetVariable(VariableSpace space, const c
*** 299,305 ****
   * get called before any user-supplied value is assigned.
   */
  void
! SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook)
  {
  	struct _variable *current,
  			   *previous;
--- 369,376 ----
   * get called before any user-supplied value is assigned.
   */
  void
! SetVariableAssignHook(VariableSpace space, const char *name,
! 					  VariableAssignHook hook)
  {
  	struct _variable *current,
  			   *previous;
*************** SetVariableAssignHook(VariableSpace spac
*** 327,332 ****
--- 398,404 ----
  	current = pg_malloc(sizeof *current);
  	current->name = pg_strdup(name);
  	current->value = NULL;
+ 	current->substitute_hook = NULL;
  	current->assign_hook = hook;
  	current->next = NULL;
  	previous->next = current;
*************** SetVariableBool(VariableSpace space, con
*** 351,392 ****
  bool
  DeleteVariable(VariableSpace space, const char *name)
  {
! 	struct _variable *current,
! 			   *previous;
! 
! 	if (!space)
! 		return true;
! 
! 	for (previous = space, current = space->next;
! 		 current;
! 		 previous = current, current = current->next)
! 	{
! 		if (strcmp(current->name, name) == 0)
! 		{
! 			if (current->assign_hook)
! 			{
! 				/* Allow deletion only if hook is okay with NULL value */
! 				if (!(*current->assign_hook) (NULL))
! 					return false;		/* message printed by hook */
! 				if (current->value)
! 					free(current->value);
! 				current->value = NULL;
! 				/* Don't delete entry, or we'd forget the hook function */
! 			}
! 			else
! 			{
! 				/* We can delete the entry as well as its value */
! 				if (current->value)
! 					free(current->value);
! 				previous->next = current->next;
! 				free(current->name);
! 				free(current);
! 			}
! 			return true;
! 		}
! 	}
! 
! 	return true;
  }
  
  /*
--- 423,429 ----
  bool
  DeleteVariable(VariableSpace space, const char *name)
  {
! 	return SetVariable(space, name, NULL);
  }
  
  /*
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index 274b4af..f382bfd 100644
*** a/src/bin/psql/variables.h
--- b/src/bin/psql/variables.h
***************
*** 18,45 ****
   * prevent invalid values from being assigned, and can update internal C
   * variables to keep them in sync with the variable's current value.
   *
!  * A hook function is called before any attempted assignment, with the
   * proposed new value of the variable (or with NULL, if an \unset is being
   * attempted).  If it returns false, the assignment doesn't occur --- it
   * should print an error message with psql_error() to tell the user why.
   *
!  * When a hook function is installed with SetVariableAssignHook(), it is
!  * called with the variable's current value (or with NULL, if it wasn't set
   * yet).  But its return value is ignored in this case.  The hook should be
   * set before any possibly-invalid value can be assigned.
   */
  typedef bool (*VariableAssignHook) (const char *newval);
  
  /*
   * Data structure representing one variable.
   *
   * Note: if value == NULL then the variable is logically unset, but we are
!  * keeping the struct around so as not to forget about its hook function.
   */
  struct _variable
  {
  	char	   *name;
  	char	   *value;
  	VariableAssignHook assign_hook;
  	struct _variable *next;
  };
--- 18,70 ----
   * prevent invalid values from being assigned, and can update internal C
   * variables to keep them in sync with the variable's current value.
   *
!  * An assign hook function is called before any attempted assignment, with the
   * proposed new value of the variable (or with NULL, if an \unset is being
   * attempted).  If it returns false, the assignment doesn't occur --- it
   * should print an error message with psql_error() to tell the user why.
   *
!  * When an assign hook function is installed with SetVariableAssignHook(), it
!  * is called with the variable's current value (or with NULL, if it wasn't set
   * yet).  But its return value is ignored in this case.  The hook should be
   * set before any possibly-invalid value can be assigned.
   */
  typedef bool (*VariableAssignHook) (const char *newval);
  
  /*
+  * Variables can also be given "substitute hook" functions.  The substitute
+  * hook can replace values (including NULL) with other values, allowing
+  * normalization of variable contents.  For example, for a boolean variable,
+  * we wish to interpret "\unset FOO" as "\set FOO off", and we can do that
+  * by installing a substitute hook.  (We can use the same substitute hook
+  * for all bool or nearly-bool variables, which is why this responsibility
+  * isn't part of the assign hook.)
+  *
+  * The substitute hook is called before any attempted assignment, and before
+  * the assign hook if any, passing the proposed new value of the variable as a
+  * malloc'd string (or NULL, if an \unset is being attempted).  It can return
+  * the same value, or a different malloc'd string, or modify the string
+  * in-place.  It should free the passed-in value if it's not returning it.
+  * The substitute hook generally should not complain about erroneous values;
+  * that's a job for the assign hook.
+  *
+  * When a substitute hook is installed with SetVariableSubstituteHook(),
+  * it is applied to the variable's current value (typically NULL, if it wasn't
+  * set yet).  It's usually best to do that before installing the assign hook
+  * if there is one.
+  */
+ typedef char *(*VariableSubstituteHook) (char *newval);
+ 
+ /*
   * Data structure representing one variable.
   *
   * Note: if value == NULL then the variable is logically unset, but we are
!  * keeping the struct around so as not to forget about its hook function(s).
   */
  struct _variable
  {
  	char	   *name;
  	char	   *value;
+ 	VariableSubstituteHook substitute_hook;
  	VariableAssignHook assign_hook;
  	struct _variable *next;
  };
*************** int GetVariableNum(VariableSpace space,
*** 65,70 ****
--- 90,96 ----
  void		PrintVariables(VariableSpace space);
  
  bool		SetVariable(VariableSpace space, const char *name, const char *value);
+ void		SetVariableSubstituteHook(VariableSpace space, const char *name, VariableSubstituteHook hook);
  void		SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook);
  bool		SetVariableBool(VariableSpace space, const char *name);
  bool		DeleteVariable(VariableSpace space, const char *name);
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index 420825a..026a4f0 100644
*** a/src/test/regress/expected/psql.out
--- b/src/test/regress/expected/psql.out
*************** invalid variable name: "invalid/name"
*** 11,16 ****
--- 11,33 ----
  unrecognized value "foo" for "AUTOCOMMIT": boolean expected
  \set FETCH_COUNT foo
  invalid value "foo" for "FETCH_COUNT": integer expected
+ -- check handling of built-in boolean variable
+ \echo :ON_ERROR_ROLLBACK
+ off
+ \set ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \set ON_ERROR_ROLLBACK foo
+ unrecognized value "foo" for "ON_ERROR_ROLLBACK"
+ Available values are: on, off, interactive.
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \set ON_ERROR_ROLLBACK on
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \unset ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ off
  -- \gset
  select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_
  \echo :pref01_test01 :pref01_test02 :pref01_test03
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index 79624b9..d823d11 100644
*** a/src/test/regress/sql/psql.sql
--- b/src/test/regress/sql/psql.sql
***************
*** 10,15 ****
--- 10,25 ----
  -- fail: invalid value for special variable
  \set AUTOCOMMIT foo
  \set FETCH_COUNT foo
+ -- check handling of built-in boolean variable
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK foo
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK on
+ \echo :ON_ERROR_ROLLBACK
+ \unset ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
  
  -- \gset
  

diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 0574b5b..631b3f6 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -166,14 +166,6 @@ main(int argc, char *argv[])
 
 	SetVariable(pset.vars, "VERSION", PG_VERSION_STR);
 
-	/* Default values for variables */
-	SetVariableBool(pset.vars, "AUTOCOMMIT");
-	SetVariable(pset.vars, "VERBOSITY", "default");
-	SetVariable(pset.vars, "SHOW_CONTEXT", "errors");
-	SetVariable(pset.vars, "PROMPT1", DEFAULT_PROMPT1);
-	SetVariable(pset.vars, "PROMPT2", DEFAULT_PROMPT2);
-	SetVariable(pset.vars, "PROMPT3", DEFAULT_PROMPT3);
-
 	parse_psql_options(argc, argv, &options);
 
 	/*
@@ -785,6 +777,11 @@ showVersion(void)
 static bool
 autocommit_hook(const char *newval)
 {
+	if (newval == NULL)
+	{
+		psql_error("built-in variable %s cannot be unset.\n", "AUTOCOMMIT");
+		return false;
+	}
 	return ParseVariableBool(newval, "AUTOCOMMIT", &pset.autocommit);
 }
 
@@ -1002,20 +999,20 @@ EstablishVariableSpace(void)
 {
 	pset.vars = CreateVariableSpace();
 
-	SetVariableAssignHook(pset.vars, "AUTOCOMMIT", autocommit_hook);
-	SetVariableAssignHook(pset.vars, "ON_ERROR_STOP", on_error_stop_hook);
-	SetVariableAssignHook(pset.vars, "QUIET", quiet_hook);
-	SetVariableAssignHook(pset.vars, "SINGLELINE", singleline_hook);
-	SetVariableAssignHook(pset.vars, "SINGLESTEP", singlestep_hook);
-	SetVariableAssignHook(pset.vars, "FETCH_COUNT", fetch_count_hook);
-	SetVariableAssignHook(pset.vars, "ECHO", echo_hook);
-	SetVariableAssignHook(pset.vars, "ECHO_HIDDEN", echo_hidden_hook);
-	SetVariableAssignHook(pset.vars, "ON_ERROR_ROLLBACK", on_error_rollback_hook);
-	SetVariableAssignHook(pset.vars, "COMP_KEYWORD_CASE", comp_keyword_case_hook);
-	SetVariableAssignHook(pset.vars, "HISTCONTROL", histcontrol_hook);
-	SetVariableAssignHook(pset.vars, "PROMPT1", prompt1_hook);
-	SetVariableAssignHook(pset.vars, "PROMPT2", prompt2_hook);
-	SetVariableAssignHook(pset.vars, "PROMPT3", prompt3_hook);
-	SetVariableAssignHook(pset.vars, "VERBOSITY", verbosity_hook);
-	SetVariableAssignHook(pset.vars, "SHOW_CONTEXT", show_context_hook);
+	SetVariableAssignHook(pset.vars, "AUTOCOMMIT", autocommit_hook, "on");
+	SetVariableAssignHook(pset.vars, "ON_ERROR_STOP", on_error_stop_hook, "off");
+	SetVariableAssignHook(pset.vars, "QUIET", quiet_hook, "off");
+	SetVariableAssignHook(pset.vars, "SINGLELINE", singleline_hook, "off");
+	SetVariableAssignHook(pset.vars, "SINGLESTEP", singlestep_hook, "off");
+	SetVariableAssignHook(pset.vars, "FETCH_COUNT", fetch_count_hook, "-1");
+	SetVariableAssignHook(pset.vars, "ECHO", echo_hook, "none");
+	SetVariableAssignHook(pset.vars, "ECHO_HIDDEN", echo_hidden_hook, "off");
+	SetVariableAssignHook(pset.vars, "ON_ERROR_ROLLBACK", on_error_rollback_hook, "off");
+	SetVariableAssignHook(pset.vars, "COMP_KEYWORD_CASE", comp_keyword_case_hook, "preserve-upper");
+	SetVariableAssignHook(pset.vars, "HISTCONTROL", histcontrol_hook, "none");
+	SetVariableAssignHook(pset.vars, "PROMPT1", prompt1_hook, DEFAULT_PROMPT1);
+	SetVariableAssignHook(pset.vars, "PROMPT2", prompt2_hook, DEFAULT_PROMPT2);
+	SetVariableAssignHook(pset.vars, "PROMPT3", prompt3_hook, DEFAULT_PROMPT3);
+	SetVariableAssignHook(pset.vars, "VERBOSITY", verbosity_hook, "default");
+	SetVariableAssignHook(pset.vars, "SHOW_CONTEXT", show_context_hook, "errors");
 }
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index 91e4ae8..2e5c3e0 100644
--- a/src/bin/psql/variables.c
+++ b/src/bin/psql/variables.c
@@ -288,9 +288,8 @@ SetVariable(VariableSpace space, const char *name, const char *value)
 /*
  * Attach an assign hook function to the named variable.
  *
- * If the variable doesn't already exist, create it with value NULL,
- * just so we have a place to store the hook function.  (Externally,
- * this isn't different from it not being defined.)
+ * If the variable doesn't already exist, create it with init_value as the
+ * content. init_value must not be NULL.
  *
  * The hook is immediately called on the variable's current value.  This is
  * meant to let it update any derived psql state.  If the hook doesn't like
@@ -299,7 +298,10 @@ SetVariable(VariableSpace space, const char *name, const char *value)
  * get called before any user-supplied value is assigned.
  */
 void
-SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook)
+SetVariableAssignHook(VariableSpace space,
+					  const char *name,
+					  VariableAssignHook hook,
+					  const char *init_value)
 {
 	struct _variable *current,
 			   *previous;
@@ -326,11 +328,11 @@ SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook
 	/* not present, make new entry */
 	current = pg_malloc(sizeof *current);
 	current->name = pg_strdup(name);
-	current->value = NULL;
+	current->value = pg_strdup(init_value);
 	current->assign_hook = hook;
 	current->next = NULL;
 	previous->next = current;
-	(void) (*hook) (NULL);
+	(void) (*hook) (current->value);
 }
 
 /*
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index 274b4af..94e7fb8 100644
--- a/src/bin/psql/variables.h
+++ b/src/bin/psql/variables.h
@@ -24,9 +24,9 @@
  * should print an error message with psql_error() to tell the user why.
  *
  * When a hook function is installed with SetVariableAssignHook(), it is
- * called with the variable's current value (or with NULL, if it wasn't set
- * yet).  But its return value is ignored in this case.  The hook should be
- * set before any possibly-invalid value can be assigned.
+ * called with the variable's initial value, but its return value is ignored
+ * in this case.
+ * The hook should be set before any possibly-invalid value can be assigned.
  */
 typedef bool (*VariableAssignHook) (const char *newval);
 
@@ -65,7 +65,10 @@ int GetVariableNum(VariableSpace space,
 void		PrintVariables(VariableSpace space);
 
 bool		SetVariable(VariableSpace space, const char *name, const char *value);
-void		SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook);
+void		SetVariableAssignHook(VariableSpace space,
+								  const char *name,
+								  VariableAssignHook hook,
+								  const char *init_value);
 bool		SetVariableBool(VariableSpace space, const char *name);
 bool		DeleteVariable(VariableSpace space, const char *name);
 

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 4e51e90..b9c8fcc 100644
*** a/doc/src/sgml/ref/psql-ref.sgml
--- b/doc/src/sgml/ref/psql-ref.sgml
*************** EOF
*** 455,462 ****
        any, by an equal sign on the command line. To unset a variable,
        leave off the equal sign. To set a variable with an empty value,
        use the equal sign but leave off the value. These assignments are
!       done during a very early stage of start-up, so variables reserved
!       for internal purposes might get overwritten later.
        </para>
        </listitem>
      </varlistentry>
--- 455,462 ----
        any, by an equal sign on the command line. To unset a variable,
        leave off the equal sign. To set a variable with an empty value,
        use the equal sign but leave off the value. These assignments are
!       done during command line processing, so variables that reflect
!       connection state will get overwritten later.
        </para>
        </listitem>
      </varlistentry>
*************** lo_import 152801
*** 2692,2698 ****
          class="parameter">name</replaceable> to <replaceable
          class="parameter">value</replaceable>, or if more than one value
          is given, to the concatenation of all of them. If only one
!         argument is given, the variable is set with an empty value. To
          unset a variable, use the <command>\unset</command> command.
          </para>
  
--- 2692,2698 ----
          class="parameter">name</replaceable> to <replaceable
          class="parameter">value</replaceable>, or if more than one value
          is given, to the concatenation of all of them. If only one
!         argument is given, the variable is set to an empty-string value. To
          unset a variable, use the <command>\unset</command> command.
          </para>
  
*************** lo_import 152801
*** 2709,2717 ****
          </para>
  
          <para>
!         Although you are welcome to set any variable to anything you
!         want, <application>psql</application> treats several variables
!         as special. They are documented in the section about variables.
          </para>
  
          <note>
--- 2709,2719 ----
          </para>
  
          <para>
!         Certain variables are special, in that they
!         control <application>psql</application>'s behavior or are
!         automatically set to reflect connection state.  These variables are
!         documented in <xref linkend="APP-PSQL-variables"
!         endterm="APP-PSQL-variables-title">, below.
          </para>
  
          <note>
*************** testdb=&gt; <userinput>\setenv LESS -imx
*** 2835,2840 ****
--- 2837,2850 ----
          Unsets (deletes) the <application>psql</> variable <replaceable
          class="parameter">name</replaceable>.
          </para>
+ 
+         <para>
+         Most variables that control <application>psql</application>'s behavior
+         cannot be unset; instead, an <literal>\unset</> command is interpreted
+         as setting them to their default values.
+         See <xref linkend="APP-PSQL-variables"
+         endterm="APP-PSQL-variables-title">, below.
+         </para>
          </listitem>
        </varlistentry>
  
*************** bar
*** 3053,3059 ****
  
      <para>
      If you call <command>\set</command> without a second argument, the
!     variable is set, with an empty string as value. To unset (i.e., delete)
      a variable, use the command <command>\unset</command>.  To show the
      values of all variables, call <command>\set</command> without any argument.
      </para>
--- 3063,3069 ----
  
      <para>
      If you call <command>\set</command> without a second argument, the
!     variable is set to an empty-string value. To unset (i.e., delete)
      a variable, use the command <command>\unset</command>.  To show the
      values of all variables, call <command>\set</command> without any argument.
      </para>
*************** bar
*** 3082,3089 ****
      By convention, all specially treated variables' names
      consist of all upper-case ASCII letters (and possibly digits and
      underscores). To ensure maximum compatibility in the future, avoid
!     using such variable names for your own purposes. A list of all specially
!     treated variables follows.
     </para>
  
      <variablelist>
--- 3092,3114 ----
      By convention, all specially treated variables' names
      consist of all upper-case ASCII letters (and possibly digits and
      underscores). To ensure maximum compatibility in the future, avoid
!     using such variable names for your own purposes.
!    </para>
! 
!    <para>
!     Variables that control <application>psql</application>'s behavior
!     generally cannot be unset or set to invalid values.  An <literal>\unset</>
!     command is allowed but is interpreted as setting the variable to its
!     default value.  A <literal>\set</> command without a second argument is
!     interpreted as setting the variable to <literal>on</>, for control
!     variables that accept that value, and is rejected for others.  Also,
!     control variables that accept the values <literal>on</>
!     and <literal>off</> will also accept other common spellings of Boolean
!     values, such as <literal>true</> and <literal>false</>.
!    </para>
! 
!    <para>
!     The specially treated variables are:
     </para>
  
      <variablelist>
*************** bar
*** 3153,3159 ****
          <para>
          The name of the database you are currently connected to. This is
          set every time you connect to a database (including program
!         start-up), but can be unset.
          </para>
          </listitem>
        </varlistentry>
--- 3178,3184 ----
          <para>
          The name of the database you are currently connected to. This is
          set every time you connect to a database (including program
!         start-up), but can be changed or unset.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3171,3178 ****
          as it is sent to the server. The switch to select this behavior is
          <option>-e</option>. If set to <literal>errors</literal>, then only
          failed queries are displayed on standard error output. The switch
!         for this behavior is <option>-b</option>. If unset, or if set to
!         <literal>none</literal>, then no queries are displayed.
          </para>
          </listitem>
        </varlistentry>
--- 3196,3203 ----
          as it is sent to the server. The switch to select this behavior is
          <option>-e</option>. If set to <literal>errors</literal>, then only
          failed queries are displayed on standard error output. The switch
!         for this behavior is <option>-b</option>. If set to
!         <literal>none</literal> (the default), then no queries are displayed.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3187,3194 ****
          <productname>PostgreSQL</productname> internals and provide
          similar functionality in your own programs. (To select this behavior
          on program start-up, use the switch <option>-E</option>.)  If you set
!         the variable to the value <literal>noexec</literal>, the queries are
          just shown but are not actually sent to the server and executed.
          </para>
          </listitem>
        </varlistentry>
--- 3212,3220 ----
          <productname>PostgreSQL</productname> internals and provide
          similar functionality in your own programs. (To select this behavior
          on program start-up, use the switch <option>-E</option>.)  If you set
!         this variable to the value <literal>noexec</literal>, the queries are
          just shown but are not actually sent to the server and executed.
+         The default value is <literal>off</>.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3200,3206 ****
          The current client character set encoding.
          This is set every time you connect to a database (including
          program start-up), and when you change the encoding
!         with <literal>\encoding</>, but it can be unset.
          </para>
          </listitem>
        </varlistentry>
--- 3226,3232 ----
          The current client character set encoding.
          This is set every time you connect to a database (including
          program start-up), and when you change the encoding
!         with <literal>\encoding</>, but it can be changed or unset.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3209,3215 ****
          <term><varname>FETCH_COUNT</varname></term>
          <listitem>
          <para>
!         If this variable is set to an integer value &gt; 0,
          the results of <command>SELECT</command> queries are fetched
          and displayed in groups of that many rows, rather than the
          default behavior of collecting the entire result set before
--- 3235,3241 ----
          <term><varname>FETCH_COUNT</varname></term>
          <listitem>
          <para>
!         If this variable is set to an integer value greater than zero,
          the results of <command>SELECT</command> queries are fetched
          and displayed in groups of that many rows, rather than the
          default behavior of collecting the entire result set before
*************** bar
*** 3220,3225 ****
--- 3246,3258 ----
          Keep in mind that when using this feature, a query might
          fail after having already displayed some rows.
          </para>
+ 
+         <para>
+         <varname>FETCH_COUNT</varname> is ignored if it is unset or does not
+         have a positive value.  It cannot be set to a value that is not
+         syntactically an integer.
+         </para>
+ 
          <tip>
          <para>
          Although you can use any output format with this feature,
*************** bar
*** 3241,3247 ****
           list. If set to a value of <literal>ignoredups</literal>, lines
           matching the previous history line are not entered. A value of
           <literal>ignoreboth</literal> combines the two options. If
!          unset, or if set to <literal>none</literal> (the default), all lines
           read in interactive mode are saved on the history list.
          </para>
          <note>
--- 3274,3280 ----
           list. If set to a value of <literal>ignoredups</literal>, lines
           matching the previous history line are not entered. A value of
           <literal>ignoreboth</literal> combines the two options. If
!          set to <literal>none</literal> (the default), all lines
           read in interactive mode are saved on the history list.
          </para>
          <note>
*************** bar
*** 3257,3264 ****
          <term><varname>HISTFILE</varname></term>
          <listitem>
          <para>
!         The file name that will be used to store the history list. The default
!         value is <filename>~/.psql_history</filename>.  For example, putting:
  <programlisting>
  \set HISTFILE ~/.psql_history- :DBNAME
  </programlisting>
--- 3290,3301 ----
          <term><varname>HISTFILE</varname></term>
          <listitem>
          <para>
!         The file name that will be used to store the history list.  If unset,
!         the file name is taken from the <envar>PSQL_HISTORY</envar>
!         environment variable.  If that is not set either, the default
!         is <filename>~/.psql_history</filename>,
!         or <filename>%APPDATA%\postgresql\psql_history</filename> on Windows.
!         For example, putting:
  <programlisting>
  \set HISTFILE ~/.psql_history- :DBNAME
  </programlisting>
*************** bar
*** 3279,3286 ****
          <term><varname>HISTSIZE</varname></term>
          <listitem>
          <para>
!         The number of commands to store in the command history. The
!         default value is 500.
          </para>
          <note>
          <para>
--- 3316,3325 ----
          <term><varname>HISTSIZE</varname></term>
          <listitem>
          <para>
!         The maximum number of commands to store in the command history.
!         If unset, at most 500 commands are stored by default.
!         If set to a value that is negative or not an integer, no limit is
!         applied.
          </para>
          <note>
          <para>
*************** bar
*** 3297,3303 ****
          <para>
          The database server host you are currently connected to. This is
          set every time you connect to a database (including program
!         start-up), but can be unset.
          </para>
          </listitem>
        </varlistentry>
--- 3336,3342 ----
          <para>
          The database server host you are currently connected to. This is
          set every time you connect to a database (including program
!         start-up), but can be changed or unset.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3350,3356 ****
          generates an error, the error is ignored and the transaction
          continues. When set to <literal>interactive</>, such errors are only
          ignored in interactive sessions, and not when reading script
!         files. When unset or set to <literal>off</>, a statement in a
          transaction block that generates an error aborts the entire
          transaction. The error rollback mode works by issuing an
          implicit <command>SAVEPOINT</> for you, just before each command
--- 3389,3395 ----
          generates an error, the error is ignored and the transaction
          continues. When set to <literal>interactive</>, such errors are only
          ignored in interactive sessions, and not when reading script
!         files. When set to <literal>off</> (the default), a statement in a
          transaction block that generates an error aborts the entire
          transaction. The error rollback mode works by issuing an
          implicit <command>SAVEPOINT</> for you, just before each command
*************** bar
*** 3385,3391 ****
          <para>
          The database server port to which you are currently connected.
          This is set every time you connect to a database (including
!         program start-up), but can be unset.
          </para>
          </listitem>
        </varlistentry>
--- 3424,3430 ----
          <para>
          The database server port to which you are currently connected.
          This is set every time you connect to a database (including
!         program start-up), but can be changed or unset.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3458,3464 ****
          <para>
          The database user you are currently connected as. This is set
          every time you connect to a database (including program
!         start-up), but can be unset.
          </para>
          </listitem>
        </varlistentry>
--- 3497,3503 ----
          <para>
          The database user you are currently connected as. This is set
          every time you connect to a database (including program
!         start-up), but can be changed or unset.
          </para>
          </listitem>
        </varlistentry>
*************** bar
*** 3481,3487 ****
          <listitem>
          <para>
          This variable is set at program start-up to
!         reflect <application>psql</>'s version.  It can be unset or changed.
          </para>
          </listitem>
        </varlistentry>
--- 3520,3526 ----
          <listitem>
          <para>
          This variable is set at program start-up to
!         reflect <application>psql</>'s version.  It can be changed or unset.
          </para>
          </listitem>
        </varlistentry>
*************** PSQL_EDITOR_LINENUMBER_ARG='--line '
*** 4015,4020 ****
--- 4054,4060 ----
      </para>
      <para>
       The location of the history file can be set explicitly via
+      the <varname>HISTFILE</varname> <application>psql</> variable or
       the <envar>PSQL_HISTORY</envar> environment variable.
      </para>
     </listitem>
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 0574b5b..a3654e6 100644
*** a/src/bin/psql/startup.c
--- b/src/bin/psql/startup.c
*************** main(int argc, char *argv[])
*** 166,175 ****
  
  	SetVariable(pset.vars, "VERSION", PG_VERSION_STR);
  
! 	/* Default values for variables */
  	SetVariableBool(pset.vars, "AUTOCOMMIT");
- 	SetVariable(pset.vars, "VERBOSITY", "default");
- 	SetVariable(pset.vars, "SHOW_CONTEXT", "errors");
  	SetVariable(pset.vars, "PROMPT1", DEFAULT_PROMPT1);
  	SetVariable(pset.vars, "PROMPT2", DEFAULT_PROMPT2);
  	SetVariable(pset.vars, "PROMPT3", DEFAULT_PROMPT3);
--- 166,173 ----
  
  	SetVariable(pset.vars, "VERSION", PG_VERSION_STR);
  
! 	/* Default values for variables (that don't match the result of \unset) */
  	SetVariableBool(pset.vars, "AUTOCOMMIT");
  	SetVariable(pset.vars, "PROMPT1", DEFAULT_PROMPT1);
  	SetVariable(pset.vars, "PROMPT2", DEFAULT_PROMPT2);
  	SetVariable(pset.vars, "PROMPT3", DEFAULT_PROMPT3);
*************** parse_psql_options(int argc, char *argv[
*** 578,594 ****
  					if (!equal_loc)
  					{
  						if (!DeleteVariable(pset.vars, value))
! 						{
! 							fprintf(stderr, _("%s: could not delete variable \"%s\"\n"),
! 									pset.progname, value);
! 							exit(EXIT_FAILURE);
! 						}
  					}
  					else
  					{
  						*equal_loc = '\0';
  						if (!SetVariable(pset.vars, value, equal_loc + 1))
! 							exit(EXIT_FAILURE);
  					}
  
  					free(value);
--- 576,588 ----
  					if (!equal_loc)
  					{
  						if (!DeleteVariable(pset.vars, value))
! 							exit(EXIT_FAILURE); /* error already printed */
  					}
  					else
  					{
  						*equal_loc = '\0';
  						if (!SetVariable(pset.vars, value, equal_loc + 1))
! 							exit(EXIT_FAILURE); /* error already printed */
  					}
  
  					free(value);
*************** showVersion(void)
*** 777,787 ****
  
  
  /*
!  * Assign hooks for psql variables.
   *
   * This isn't an amazingly good place for them, but neither is anywhere else.
   */
  
  static bool
  autocommit_hook(const char *newval)
  {
--- 771,798 ----
  
  
  /*
!  * Substitute hooks and assign hooks for psql variables.
   *
   * This isn't an amazingly good place for them, but neither is anywhere else.
   */
  
+ static char *
+ bool_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 	{
+ 		/* "\unset FOO" becomes "\set FOO off" */
+ 		newval = pg_strdup("off");
+ 	}
+ 	else if (newval[0] == '\0')
+ 	{
+ 		/* "\set FOO" becomes "\set FOO on" */
+ 		pg_free(newval);
+ 		newval = pg_strdup("on");
+ 	}
+ 	return newval;
+ }
+ 
  static bool
  autocommit_hook(const char *newval)
  {
*************** fetch_count_hook(const char *newval)
*** 822,833 ****
  	return true;
  }
  
  static bool
  echo_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.echo = PSQL_ECHO_NONE;
! 	else if (pg_strcasecmp(newval, "queries") == 0)
  		pset.echo = PSQL_ECHO_QUERIES;
  	else if (pg_strcasecmp(newval, "errors") == 0)
  		pset.echo = PSQL_ECHO_ERRORS;
--- 833,851 ----
  	return true;
  }
  
+ static char *
+ echo_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("none");
+ 	return newval;
+ }
+ 
  static bool
  echo_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "queries") == 0)
  		pset.echo = PSQL_ECHO_QUERIES;
  	else if (pg_strcasecmp(newval, "errors") == 0)
  		pset.echo = PSQL_ECHO_ERRORS;
*************** echo_hook(const char *newval)
*** 846,854 ****
  static bool
  echo_hidden_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.echo_hidden = PSQL_ECHO_HIDDEN_OFF;
! 	else if (pg_strcasecmp(newval, "noexec") == 0)
  		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
  	else
  	{
--- 864,871 ----
  static bool
  echo_hidden_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "noexec") == 0)
  		pset.echo_hidden = PSQL_ECHO_HIDDEN_NOEXEC;
  	else
  	{
*************** echo_hidden_hook(const char *newval)
*** 868,876 ****
  static bool
  on_error_rollback_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_OFF;
! 	else if (pg_strcasecmp(newval, "interactive") == 0)
  		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
  	else
  	{
--- 885,892 ----
  static bool
  on_error_rollback_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "interactive") == 0)
  		pset.on_error_rollback = PSQL_ERROR_ROLLBACK_INTERACTIVE;
  	else
  	{
*************** on_error_rollback_hook(const char *newva
*** 887,898 ****
  	return true;
  }
  
  static bool
  comp_keyword_case_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
! 	else if (pg_strcasecmp(newval, "preserve-upper") == 0)
  		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
  	else if (pg_strcasecmp(newval, "preserve-lower") == 0)
  		pset.comp_case = PSQL_COMP_CASE_PRESERVE_LOWER;
--- 903,921 ----
  	return true;
  }
  
+ static char *
+ comp_keyword_case_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("preserve-upper");
+ 	return newval;
+ }
+ 
  static bool
  comp_keyword_case_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "preserve-upper") == 0)
  		pset.comp_case = PSQL_COMP_CASE_PRESERVE_UPPER;
  	else if (pg_strcasecmp(newval, "preserve-lower") == 0)
  		pset.comp_case = PSQL_COMP_CASE_PRESERVE_LOWER;
*************** comp_keyword_case_hook(const char *newva
*** 909,920 ****
  	return true;
  }
  
  static bool
  histcontrol_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.histcontrol = hctl_none;
! 	else if (pg_strcasecmp(newval, "ignorespace") == 0)
  		pset.histcontrol = hctl_ignorespace;
  	else if (pg_strcasecmp(newval, "ignoredups") == 0)
  		pset.histcontrol = hctl_ignoredups;
--- 932,950 ----
  	return true;
  }
  
+ static char *
+ histcontrol_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("none");
+ 	return newval;
+ }
+ 
  static bool
  histcontrol_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "ignorespace") == 0)
  		pset.histcontrol = hctl_ignorespace;
  	else if (pg_strcasecmp(newval, "ignoredups") == 0)
  		pset.histcontrol = hctl_ignoredups;
*************** prompt3_hook(const char *newval)
*** 952,963 ****
  	return true;
  }
  
  static bool
  verbosity_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.verbosity = PQERRORS_DEFAULT;
! 	else if (pg_strcasecmp(newval, "default") == 0)
  		pset.verbosity = PQERRORS_DEFAULT;
  	else if (pg_strcasecmp(newval, "terse") == 0)
  		pset.verbosity = PQERRORS_TERSE;
--- 982,1000 ----
  	return true;
  }
  
+ static char *
+ verbosity_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("default");
+ 	return newval;
+ }
+ 
  static bool
  verbosity_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "default") == 0)
  		pset.verbosity = PQERRORS_DEFAULT;
  	else if (pg_strcasecmp(newval, "terse") == 0)
  		pset.verbosity = PQERRORS_TERSE;
*************** verbosity_hook(const char *newval)
*** 974,985 ****
  	return true;
  }
  
  static bool
  show_context_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.show_context = PQSHOW_CONTEXT_ERRORS;
! 	else if (pg_strcasecmp(newval, "never") == 0)
  		pset.show_context = PQSHOW_CONTEXT_NEVER;
  	else if (pg_strcasecmp(newval, "errors") == 0)
  		pset.show_context = PQSHOW_CONTEXT_ERRORS;
--- 1011,1029 ----
  	return true;
  }
  
+ static char *
+ show_context_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("errors");
+ 	return newval;
+ }
+ 
  static bool
  show_context_hook(const char *newval)
  {
! 	Assert(newval != NULL);		/* else substitute hook messed up */
! 	if (pg_strcasecmp(newval, "never") == 0)
  		pset.show_context = PQSHOW_CONTEXT_NEVER;
  	else if (pg_strcasecmp(newval, "errors") == 0)
  		pset.show_context = PQSHOW_CONTEXT_ERRORS;
*************** EstablishVariableSpace(void)
*** 1002,1021 ****
  {
  	pset.vars = CreateVariableSpace();
  
! 	SetVariableAssignHook(pset.vars, "AUTOCOMMIT", autocommit_hook);
! 	SetVariableAssignHook(pset.vars, "ON_ERROR_STOP", on_error_stop_hook);
! 	SetVariableAssignHook(pset.vars, "QUIET", quiet_hook);
! 	SetVariableAssignHook(pset.vars, "SINGLELINE", singleline_hook);
! 	SetVariableAssignHook(pset.vars, "SINGLESTEP", singlestep_hook);
! 	SetVariableAssignHook(pset.vars, "FETCH_COUNT", fetch_count_hook);
! 	SetVariableAssignHook(pset.vars, "ECHO", echo_hook);
! 	SetVariableAssignHook(pset.vars, "ECHO_HIDDEN", echo_hidden_hook);
! 	SetVariableAssignHook(pset.vars, "ON_ERROR_ROLLBACK", on_error_rollback_hook);
! 	SetVariableAssignHook(pset.vars, "COMP_KEYWORD_CASE", comp_keyword_case_hook);
! 	SetVariableAssignHook(pset.vars, "HISTCONTROL", histcontrol_hook);
! 	SetVariableAssignHook(pset.vars, "PROMPT1", prompt1_hook);
! 	SetVariableAssignHook(pset.vars, "PROMPT2", prompt2_hook);
! 	SetVariableAssignHook(pset.vars, "PROMPT3", prompt3_hook);
! 	SetVariableAssignHook(pset.vars, "VERBOSITY", verbosity_hook);
! 	SetVariableAssignHook(pset.vars, "SHOW_CONTEXT", show_context_hook);
  }
--- 1046,1097 ----
  {
  	pset.vars = CreateVariableSpace();
  
! 	SetVariableHooks(pset.vars, "AUTOCOMMIT",
! 					 bool_substitute_hook,
! 					 autocommit_hook);
! 	SetVariableHooks(pset.vars, "ON_ERROR_STOP",
! 					 bool_substitute_hook,
! 					 on_error_stop_hook);
! 	SetVariableHooks(pset.vars, "QUIET",
! 					 bool_substitute_hook,
! 					 quiet_hook);
! 	SetVariableHooks(pset.vars, "SINGLELINE",
! 					 bool_substitute_hook,
! 					 singleline_hook);
! 	SetVariableHooks(pset.vars, "SINGLESTEP",
! 					 bool_substitute_hook,
! 					 singlestep_hook);
! 	SetVariableHooks(pset.vars, "FETCH_COUNT",
! 					 NULL,
! 					 fetch_count_hook);
! 	SetVariableHooks(pset.vars, "ECHO",
! 					 echo_substitute_hook,
! 					 echo_hook);
! 	SetVariableHooks(pset.vars, "ECHO_HIDDEN",
! 					 bool_substitute_hook,
! 					 echo_hidden_hook);
! 	SetVariableHooks(pset.vars, "ON_ERROR_ROLLBACK",
! 					 bool_substitute_hook,
! 					 on_error_rollback_hook);
! 	SetVariableHooks(pset.vars, "COMP_KEYWORD_CASE",
! 					 comp_keyword_case_substitute_hook,
! 					 comp_keyword_case_hook);
! 	SetVariableHooks(pset.vars, "HISTCONTROL",
! 					 histcontrol_substitute_hook,
! 					 histcontrol_hook);
! 	SetVariableHooks(pset.vars, "PROMPT1",
! 					 NULL,
! 					 prompt1_hook);
! 	SetVariableHooks(pset.vars, "PROMPT2",
! 					 NULL,
! 					 prompt2_hook);
! 	SetVariableHooks(pset.vars, "PROMPT3",
! 					 NULL,
! 					 prompt3_hook);
! 	SetVariableHooks(pset.vars, "VERBOSITY",
! 					 verbosity_substitute_hook,
! 					 verbosity_hook);
! 	SetVariableHooks(pset.vars, "SHOW_CONTEXT",
! 					 show_context_substitute_hook,
! 					 show_context_hook);
  }
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index 91e4ae8..b9b8fcb 100644
*** a/src/bin/psql/variables.c
--- b/src/bin/psql/variables.c
*************** CreateVariableSpace(void)
*** 52,57 ****
--- 52,58 ----
  	ptr = pg_malloc(sizeof *ptr);
  	ptr->name = NULL;
  	ptr->value = NULL;
+ 	ptr->substitute_hook = NULL;
  	ptr->assign_hook = NULL;
  	ptr->next = NULL;
  
*************** ParseVariableBool(const char *value, con
*** 101,111 ****
  	size_t		len;
  	bool		valid = true;
  
  	if (value == NULL)
! 	{
! 		*result = false;		/* not set -> assume "off" */
! 		return valid;
! 	}
  
  	len = strlen(value);
  
--- 102,110 ----
  	size_t		len;
  	bool		valid = true;
  
+ 	/* Treat "unset" as an empty string, which will lead to error below */
  	if (value == NULL)
! 		value = "";
  
  	len = strlen(value);
  
*************** ParseVariableNum(const char *value, cons
*** 152,159 ****
  	char	   *end;
  	long		numval;
  
  	if (value == NULL)
! 		return false;
  	errno = 0;
  	numval = strtol(value, &end, 0);
  	if (errno == 0 && *end == '\0' && end != value && numval == (int) numval)
--- 151,160 ----
  	char	   *end;
  	long		numval;
  
+ 	/* Treat "unset" as an empty string, which will lead to error below */
  	if (value == NULL)
! 		value = "";
! 
  	errno = 0;
  	numval = strtol(value, &end, 0);
  	if (errno == 0 && *end == '\0' && end != value && numval == (int) numval)
*************** SetVariable(VariableSpace space, const c
*** 235,247 ****
  
  	if (!valid_variable_name(name))
  	{
  		psql_error("invalid variable name: \"%s\"\n", name);
  		return false;
  	}
  
- 	if (!value)
- 		return DeleteVariable(space, name);
- 
  	for (previous = space, current = space->next;
  		 current;
  		 previous = current, current = current->next)
--- 236,248 ----
  
  	if (!valid_variable_name(name))
  	{
+ 		/* Deletion of non-existent variable is not an error */
+ 		if (!value)
+ 			return true;
  		psql_error("invalid variable name: \"%s\"\n", name);
  		return false;
  	}
  
  	for (previous = space, current = space->next;
  		 current;
  		 previous = current, current = current->next)
*************** SetVariable(VariableSpace space, const c
*** 249,262 ****
  		if (strcmp(current->name, name) == 0)
  		{
  			/*
! 			 * Found entry, so update, unless hook returns false.  The hook
! 			 * may need the passed value to have the same lifespan as the
! 			 * variable, so allocate it right away, even though we'll have to
! 			 * free it again if the hook returns false.
  			 */
! 			char	   *new_value = pg_strdup(value);
  			bool		confirmed;
  
  			if (current->assign_hook)
  				confirmed = (*current->assign_hook) (new_value);
  			else
--- 250,269 ----
  		if (strcmp(current->name, name) == 0)
  		{
  			/*
! 			 * Found entry, so update, unless assign hook returns false.
! 			 *
! 			 * We must duplicate the passed value to start with.  This
! 			 * simplifies the API for substitute hooks.  Moreover, some assign
! 			 * hooks assume that the passed value has the same lifespan as the
! 			 * variable.  Having to free the string again on failure is a
! 			 * small price to pay for keeping these APIs simple.
  			 */
! 			char	   *new_value = value ? pg_strdup(value) : NULL;
  			bool		confirmed;
  
+ 			if (current->substitute_hook)
+ 				new_value = (*current->substitute_hook) (new_value);
+ 
  			if (current->assign_hook)
  				confirmed = (*current->assign_hook) (new_value);
  			else
*************** SetVariable(VariableSpace space, const c
*** 267,305 ****
  				if (current->value)
  					pg_free(current->value);
  				current->value = new_value;
  			}
! 			else
  				pg_free(new_value);		/* current->value is left unchanged */
  
  			return confirmed;
  		}
  	}
  
! 	/* not present, make new entry */
! 	current = pg_malloc(sizeof *current);
! 	current->name = pg_strdup(name);
! 	current->value = pg_strdup(value);
! 	current->assign_hook = NULL;
! 	current->next = NULL;
! 	previous->next = current;
  	return true;
  }
  
  /*
!  * Attach an assign hook function to the named variable.
   *
!  * If the variable doesn't already exist, create it with value NULL,
!  * just so we have a place to store the hook function.  (Externally,
!  * this isn't different from it not being defined.)
   *
!  * The hook is immediately called on the variable's current value.  This is
!  * meant to let it update any derived psql state.  If the hook doesn't like
!  * the current value, it will print a message to that effect, but we'll ignore
!  * it.  Generally we do not expect any such failure here, because this should
!  * get called before any user-supplied value is assigned.
   */
  void
! SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook)
  {
  	struct _variable *current,
  			   *previous;
--- 274,334 ----
  				if (current->value)
  					pg_free(current->value);
  				current->value = new_value;
+ 
+ 				/*
+ 				 * If we deleted the value, and there are no hooks to
+ 				 * remember, we can discard the variable altogether.
+ 				 */
+ 				if (new_value == NULL &&
+ 					current->substitute_hook == NULL &&
+ 					current->assign_hook == NULL)
+ 				{
+ 					previous->next = current->next;
+ 					free(current->name);
+ 					free(current);
+ 				}
  			}
! 			else if (new_value)
  				pg_free(new_value);		/* current->value is left unchanged */
  
  			return confirmed;
  		}
  	}
  
! 	/* not present, make new entry ... unless we were asked to delete */
! 	if (value)
! 	{
! 		current = pg_malloc(sizeof *current);
! 		current->name = pg_strdup(name);
! 		current->value = pg_strdup(value);
! 		current->substitute_hook = NULL;
! 		current->assign_hook = NULL;
! 		current->next = NULL;
! 		previous->next = current;
! 	}
  	return true;
  }
  
  /*
!  * Attach substitute and/or assign hook functions to the named variable.
!  * If you need only one hook, pass NULL for the other.
   *
!  * If the variable doesn't already exist, create it with value NULL, just so
!  * we have a place to store the hook function(s).  (The substitute hook might
!  * immediately change the NULL to something else; if not, this state is
!  * externally the same as the variable not being defined.)
   *
!  * The substitute hook, if given, is immediately called on the variable's
!  * value.  Then the assign hook, if given, is called on the variable's value.
!  * This is meant to let it update any derived psql state.  If the assign hook
!  * doesn't like the current value, it will print a message to that effect,
!  * but we'll ignore it.  Generally we do not expect any such failure here,
!  * because this should get called before any user-supplied value is assigned.
   */
  void
! SetVariableHooks(VariableSpace space, const char *name,
! 				 VariableSubstituteHook shook,
! 				 VariableAssignHook ahook)
  {
  	struct _variable *current,
  			   *previous;
*************** SetVariableAssignHook(VariableSpace spac
*** 317,324 ****
  		if (strcmp(current->name, name) == 0)
  		{
  			/* found entry, so update */
! 			current->assign_hook = hook;
! 			(void) (*hook) (current->value);
  			return;
  		}
  	}
--- 346,357 ----
  		if (strcmp(current->name, name) == 0)
  		{
  			/* found entry, so update */
! 			current->substitute_hook = shook;
! 			current->assign_hook = ahook;
! 			if (shook)
! 				current->value = (*shook) (current->value);
! 			if (ahook)
! 				(void) (*ahook) (current->value);
  			return;
  		}
  	}
*************** SetVariableAssignHook(VariableSpace spac
*** 327,336 ****
  	current = pg_malloc(sizeof *current);
  	current->name = pg_strdup(name);
  	current->value = NULL;
! 	current->assign_hook = hook;
  	current->next = NULL;
  	previous->next = current;
! 	(void) (*hook) (NULL);
  }
  
  /*
--- 360,373 ----
  	current = pg_malloc(sizeof *current);
  	current->name = pg_strdup(name);
  	current->value = NULL;
! 	current->substitute_hook = shook;
! 	current->assign_hook = ahook;
  	current->next = NULL;
  	previous->next = current;
! 	if (shook)
! 		current->value = (*shook) (current->value);
! 	if (ahook)
! 		(void) (*ahook) (current->value);
  }
  
  /*
*************** SetVariableBool(VariableSpace space, con
*** 351,392 ****
  bool
  DeleteVariable(VariableSpace space, const char *name)
  {
! 	struct _variable *current,
! 			   *previous;
! 
! 	if (!space)
! 		return true;
! 
! 	for (previous = space, current = space->next;
! 		 current;
! 		 previous = current, current = current->next)
! 	{
! 		if (strcmp(current->name, name) == 0)
! 		{
! 			if (current->assign_hook)
! 			{
! 				/* Allow deletion only if hook is okay with NULL value */
! 				if (!(*current->assign_hook) (NULL))
! 					return false;		/* message printed by hook */
! 				if (current->value)
! 					free(current->value);
! 				current->value = NULL;
! 				/* Don't delete entry, or we'd forget the hook function */
! 			}
! 			else
! 			{
! 				/* We can delete the entry as well as its value */
! 				if (current->value)
! 					free(current->value);
! 				previous->next = current->next;
! 				free(current->name);
! 				free(current);
! 			}
! 			return true;
! 		}
! 	}
! 
! 	return true;
  }
  
  /*
--- 388,394 ----
  bool
  DeleteVariable(VariableSpace space, const char *name)
  {
! 	return SetVariable(space, name, NULL);
  }
  
  /*
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index 274b4af..84be780 100644
*** a/src/bin/psql/variables.h
--- b/src/bin/psql/variables.h
***************
*** 18,29 ****
   * prevent invalid values from being assigned, and can update internal C
   * variables to keep them in sync with the variable's current value.
   *
!  * A hook function is called before any attempted assignment, with the
   * proposed new value of the variable (or with NULL, if an \unset is being
   * attempted).  If it returns false, the assignment doesn't occur --- it
   * should print an error message with psql_error() to tell the user why.
   *
!  * When a hook function is installed with SetVariableAssignHook(), it is
   * called with the variable's current value (or with NULL, if it wasn't set
   * yet).  But its return value is ignored in this case.  The hook should be
   * set before any possibly-invalid value can be assigned.
--- 18,29 ----
   * prevent invalid values from being assigned, and can update internal C
   * variables to keep them in sync with the variable's current value.
   *
!  * An assign hook function is called before any attempted assignment, with the
   * proposed new value of the variable (or with NULL, if an \unset is being
   * attempted).  If it returns false, the assignment doesn't occur --- it
   * should print an error message with psql_error() to tell the user why.
   *
!  * When an assign hook function is installed with SetVariableHooks(), it is
   * called with the variable's current value (or with NULL, if it wasn't set
   * yet).  But its return value is ignored in this case.  The hook should be
   * set before any possibly-invalid value can be assigned.
***************
*** 31,45 ****
  typedef bool (*VariableAssignHook) (const char *newval);
  
  /*
   * Data structure representing one variable.
   *
   * Note: if value == NULL then the variable is logically unset, but we are
!  * keeping the struct around so as not to forget about its hook function.
   */
  struct _variable
  {
  	char	   *name;
  	char	   *value;
  	VariableAssignHook assign_hook;
  	struct _variable *next;
  };
--- 31,69 ----
  typedef bool (*VariableAssignHook) (const char *newval);
  
  /*
+  * Variables can also be given "substitute hook" functions.  The substitute
+  * hook can replace values (including NULL) with other values, allowing
+  * normalization of variable contents.  For example, for a boolean variable,
+  * we wish to interpret "\unset FOO" as "\set FOO off", and we can do that
+  * by installing a substitute hook.  (We can use the same substitute hook
+  * for all bool or nearly-bool variables, which is why this responsibility
+  * isn't part of the assign hook.)
+  *
+  * The substitute hook is called before any attempted assignment, and before
+  * the assign hook if any, passing the proposed new value of the variable as a
+  * malloc'd string (or NULL, if an \unset is being attempted).  It can return
+  * the same value, or a different malloc'd string, or modify the string
+  * in-place.  It should free the passed-in value if it's not returning it.
+  * The substitute hook generally should not complain about erroneous values;
+  * that's a job for the assign hook.
+  *
+  * When a substitute hook is installed with SetVariableHooks(), it is applied
+  * to the variable's current value (typically NULL, if it wasn't set yet).
+  * That also happens before applying the assign hook.
+  */
+ typedef char *(*VariableSubstituteHook) (char *newval);
+ 
+ /*
   * Data structure representing one variable.
   *
   * Note: if value == NULL then the variable is logically unset, but we are
!  * keeping the struct around so as not to forget about its hook function(s).
   */
  struct _variable
  {
  	char	   *name;
  	char	   *value;
+ 	VariableSubstituteHook substitute_hook;
  	VariableAssignHook assign_hook;
  	struct _variable *next;
  };
*************** int GetVariableNum(VariableSpace space,
*** 65,74 ****
  void		PrintVariables(VariableSpace space);
  
  bool		SetVariable(VariableSpace space, const char *name, const char *value);
- void		SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook);
  bool		SetVariableBool(VariableSpace space, const char *name);
  bool		DeleteVariable(VariableSpace space, const char *name);
  
  void		PsqlVarEnumError(const char *name, const char *value, const char *suggestions);
  
  #endif   /* VARIABLES_H */
--- 89,101 ----
  void		PrintVariables(VariableSpace space);
  
  bool		SetVariable(VariableSpace space, const char *name, const char *value);
  bool		SetVariableBool(VariableSpace space, const char *name);
  bool		DeleteVariable(VariableSpace space, const char *name);
  
+ void SetVariableHooks(VariableSpace space, const char *name,
+ 				 VariableSubstituteHook shook,
+ 				 VariableAssignHook ahook);
+ 
  void		PsqlVarEnumError(const char *name, const char *value, const char *suggestions);
  
  #endif   /* VARIABLES_H */
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index 420825a..026a4f0 100644
*** a/src/test/regress/expected/psql.out
--- b/src/test/regress/expected/psql.out
*************** invalid variable name: "invalid/name"
*** 11,16 ****
--- 11,33 ----
  unrecognized value "foo" for "AUTOCOMMIT": boolean expected
  \set FETCH_COUNT foo
  invalid value "foo" for "FETCH_COUNT": integer expected
+ -- check handling of built-in boolean variable
+ \echo :ON_ERROR_ROLLBACK
+ off
+ \set ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \set ON_ERROR_ROLLBACK foo
+ unrecognized value "foo" for "ON_ERROR_ROLLBACK"
+ Available values are: on, off, interactive.
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \set ON_ERROR_ROLLBACK on
+ \echo :ON_ERROR_ROLLBACK
+ on
+ \unset ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ off
  -- \gset
  select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_
  \echo :pref01_test01 :pref01_test02 :pref01_test03
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index 79624b9..d823d11 100644
*** a/src/test/regress/sql/psql.sql
--- b/src/test/regress/sql/psql.sql
***************
*** 10,15 ****
--- 10,25 ----
  -- fail: invalid value for special variable
  \set AUTOCOMMIT foo
  \set FETCH_COUNT foo
+ -- check handling of built-in boolean variable
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK foo
+ \echo :ON_ERROR_ROLLBACK
+ \set ON_ERROR_ROLLBACK on
+ \echo :ON_ERROR_ROLLBACK
+ \unset ON_ERROR_ROLLBACK
+ \echo :ON_ERROR_ROLLBACK
  
  -- \gset
  

diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index b9b8fcb..9ca1000 100644
*** a/src/bin/psql/variables.c
--- b/src/bin/psql/variables.c
*************** valid_variable_name(const char *name)
*** 43,48 ****
--- 43,51 ----
  /*
   * A "variable space" is represented by an otherwise-unused struct _variable
   * that serves as list header.
+  *
+  * The list entries are kept in name order (according to strcmp).  This
+  * is mainly to make the results of PrintVariables() more pleasing.
   */
  VariableSpace
  CreateVariableSpace(void)
*************** GetVariable(VariableSpace space, const c
*** 74,84 ****
  
  	for (current = space->next; current; current = current->next)
  	{
! 		if (strcmp(current->name, name) == 0)
  		{
  			/* this is correct answer when value is NULL, too */
  			return current->value;
  		}
  	}
  
  	return NULL;
--- 77,91 ----
  
  	for (current = space->next; current; current = current->next)
  	{
! 		int			cmp = strcmp(current->name, name);
! 
! 		if (cmp == 0)
  		{
  			/* this is correct answer when value is NULL, too */
  			return current->value;
  		}
+ 		if (cmp > 0)
+ 			break;				/* it's not there */
  	}
  
  	return NULL;
*************** SetVariable(VariableSpace space, const c
*** 247,253 ****
  		 current;
  		 previous = current, current = current->next)
  	{
! 		if (strcmp(current->name, name) == 0)
  		{
  			/*
  			 * Found entry, so update, unless assign hook returns false.
--- 254,262 ----
  		 current;
  		 previous = current, current = current->next)
  	{
! 		int			cmp = strcmp(current->name, name);
! 
! 		if (cmp == 0)
  		{
  			/*
  			 * Found entry, so update, unless assign hook returns false.
*************** SetVariable(VariableSpace space, const c
*** 293,298 ****
--- 302,309 ----
  
  			return confirmed;
  		}
+ 		if (cmp > 0)
+ 			break;				/* it's not there */
  	}
  
  	/* not present, make new entry ... unless we were asked to delete */
*************** SetVariable(VariableSpace space, const c
*** 303,309 ****
  		current->value = pg_strdup(value);
  		current->substitute_hook = NULL;
  		current->assign_hook = NULL;
! 		current->next = NULL;
  		previous->next = current;
  	}
  	return true;
--- 314,320 ----
  		current->value = pg_strdup(value);
  		current->substitute_hook = NULL;
  		current->assign_hook = NULL;
! 		current->next = previous->next;
  		previous->next = current;
  	}
  	return true;
*************** SetVariableHooks(VariableSpace space, co
*** 343,349 ****
  		 current;
  		 previous = current, current = current->next)
  	{
! 		if (strcmp(current->name, name) == 0)
  		{
  			/* found entry, so update */
  			current->substitute_hook = shook;
--- 354,362 ----
  		 current;
  		 previous = current, current = current->next)
  	{
! 		int			cmp = strcmp(current->name, name);
! 
! 		if (cmp == 0)
  		{
  			/* found entry, so update */
  			current->substitute_hook = shook;
*************** SetVariableHooks(VariableSpace space, co
*** 354,359 ****
--- 367,374 ----
  				(void) (*ahook) (current->value);
  			return;
  		}
+ 		if (cmp > 0)
+ 			break;				/* it's not there */
  	}
  
  	/* not present, make new entry */
*************** SetVariableHooks(VariableSpace space, co
*** 362,368 ****
  	current->value = NULL;
  	current->substitute_hook = shook;
  	current->assign_hook = ahook;
! 	current->next = NULL;
  	previous->next = current;
  	if (shook)
  		current->value = (*shook) (current->value);
--- 377,383 ----
  	current->value = NULL;
  	current->substitute_hook = shook;
  	current->assign_hook = ahook;
! 	current->next = previous->next;
  	previous->next = current;
  	if (shook)
  		current->value = (*shook) (current->value);

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index b9c8fcc..ae58708 100644
*** a/doc/src/sgml/ref/psql-ref.sgml
--- b/doc/src/sgml/ref/psql-ref.sgml
*************** bar
*** 3247,3258 ****
          fail after having already displayed some rows.
          </para>
  
-         <para>
-         <varname>FETCH_COUNT</varname> is ignored if it is unset or does not
-         have a positive value.  It cannot be set to a value that is not
-         syntactically an integer.
-         </para>
- 
          <tip>
          <para>
          Although you can use any output format with this feature,
--- 3247,3252 ----
*************** bar
*** 3316,3325 ****
          <term><varname>HISTSIZE</varname></term>
          <listitem>
          <para>
!         The maximum number of commands to store in the command history.
!         If unset, at most 500 commands are stored by default.
!         If set to a value that is negative or not an integer, no limit is
!         applied.
          </para>
          <note>
          <para>
--- 3310,3317 ----
          <term><varname>HISTSIZE</varname></term>
          <listitem>
          <para>
!         The maximum number of commands to store in the command history
!         (default 500).  If set to a negative value, no limit is applied.
          </para>
          <note>
          <para>
*************** bar
*** 3345,3357 ****
          <term><varname>IGNOREEOF</varname></term>
          <listitem>
          <para>
!          If unset, sending an <acronym>EOF</> character (usually
           <keycombo action="simul"><keycap>Control</><keycap>D</></>)
           to an interactive session of <application>psql</application>
!          will terminate the application. If set to a numeric value,
!          that many <acronym>EOF</> characters are ignored before the
!          application terminates.  If the variable is set but not to a
!          numeric value, the default is 10.
          </para>
          <note>
          <para>
--- 3337,3349 ----
          <term><varname>IGNOREEOF</varname></term>
          <listitem>
          <para>
!          If set to 1 or less, sending an <acronym>EOF</> character (usually
           <keycombo action="simul"><keycap>Control</><keycap>D</></>)
           to an interactive session of <application>psql</application>
!          will terminate the application.  If set to a larger numeric value,
!          that many consecutive <acronym>EOF</> characters must be typed to
!          make an interactive session terminate.  If the variable is set to a
!          non-numeric value, it is interpreted as 10.
          </para>
          <note>
          <para>
diff --git a/src/bin/psql/help.c b/src/bin/psql/help.c
index 5365629..3e3cab4 100644
*** a/src/bin/psql/help.c
--- b/src/bin/psql/help.c
*************** helpVariables(unsigned short int pager)
*** 348,356 ****
  					  "                     (default: 0=unlimited)\n"));
  	fprintf(output, _("  HISTCONTROL        controls command history [ignorespace, ignoredups, ignoreboth]\n"));
  	fprintf(output, _("  HISTFILE           file name used to store the command history\n"));
! 	fprintf(output, _("  HISTSIZE           the number of commands to store in the command history\n"));
  	fprintf(output, _("  HOST               the currently connected database server host\n"));
! 	fprintf(output, _("  IGNOREEOF          if unset, sending an EOF to interactive session terminates application\n"));
  	fprintf(output, _("  LASTOID            value of the last affected OID\n"));
  	fprintf(output, _("  ON_ERROR_ROLLBACK  if set, an error doesn't stop a transaction (uses implicit savepoints)\n"));
  	fprintf(output, _("  ON_ERROR_STOP      stop batch execution after error\n"));
--- 348,356 ----
  					  "                     (default: 0=unlimited)\n"));
  	fprintf(output, _("  HISTCONTROL        controls command history [ignorespace, ignoredups, ignoreboth]\n"));
  	fprintf(output, _("  HISTFILE           file name used to store the command history\n"));
! 	fprintf(output, _("  HISTSIZE           max number of commands to store in the command history\n"));
  	fprintf(output, _("  HOST               the currently connected database server host\n"));
! 	fprintf(output, _("  IGNOREEOF          number of EOFs needed to terminate an interactive session\n"));
  	fprintf(output, _("  LASTOID            value of the last affected OID\n"));
  	fprintf(output, _("  ON_ERROR_ROLLBACK  if set, an error doesn't stop a transaction (uses implicit savepoints)\n"));
  	fprintf(output, _("  ON_ERROR_STOP      stop batch execution after error\n"));
diff --git a/src/bin/psql/input.c b/src/bin/psql/input.c
index 3e3e97a..b8c9a00 100644
*** a/src/bin/psql/input.c
--- b/src/bin/psql/input.c
*************** finishInput(void)
*** 539,548 ****
  #ifdef USE_READLINE
  	if (useHistory && psql_history)
  	{
! 		int			hist_size;
! 
! 		hist_size = GetVariableNum(pset.vars, "HISTSIZE", 500, -1);
! 		(void) saveHistory(psql_history, hist_size);
  		free(psql_history);
  		psql_history = NULL;
  	}
--- 539,545 ----
  #ifdef USE_READLINE
  	if (useHistory && psql_history)
  	{
! 		(void) saveHistory(psql_history, pset.histsize);
  		free(psql_history);
  		psql_history = NULL;
  	}
diff --git a/src/bin/psql/mainloop.c b/src/bin/psql/mainloop.c
index dc25b4b..6e358e2 100644
*** a/src/bin/psql/mainloop.c
--- b/src/bin/psql/mainloop.c
*************** MainLoop(FILE *source)
*** 162,168 ****
  				/* This tries to mimic bash's IGNOREEOF feature. */
  				count_eof++;
  
! 				if (count_eof < GetVariableNum(pset.vars, "IGNOREEOF", 0, 10))
  				{
  					if (!pset.quiet)
  						printf(_("Use \"\\q\" to leave %s.\n"), pset.progname);
--- 162,168 ----
  				/* This tries to mimic bash's IGNOREEOF feature. */
  				count_eof++;
  
! 				if (count_eof < pset.ignoreeof)
  				{
  					if (!pset.quiet)
  						printf(_("Use \"\\q\" to leave %s.\n"), pset.progname);
diff --git a/src/bin/psql/settings.h b/src/bin/psql/settings.h
index 4c7c3b1..195f5a1 100644
*** a/src/bin/psql/settings.h
--- b/src/bin/psql/settings.h
*************** typedef struct _psqlSettings
*** 125,130 ****
--- 125,132 ----
  	bool		singleline;
  	bool		singlestep;
  	int			fetch_count;
+ 	int			histsize;
+ 	int			ignoreeof;
  	PSQL_ECHO	echo;
  	PSQL_ECHO_HIDDEN echo_hidden;
  	PSQL_ERROR_ROLLBACK on_error_rollback;
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index a3654e6..88d686a 100644
*** a/src/bin/psql/startup.c
--- b/src/bin/psql/startup.c
*************** showVersion(void)
*** 774,779 ****
--- 774,784 ----
   * Substitute hooks and assign hooks for psql variables.
   *
   * This isn't an amazingly good place for them, but neither is anywhere else.
+  *
+  * By policy, every special variable that controls any psql behavior should
+  * have one or both hooks, even if they're just no-ops.  This ensures that
+  * the variable will remain present in variables.c's list even when unset,
+  * which ensures that it's known to tab completion.
   */
  
  static char *
*************** singlestep_hook(const char *newval)
*** 823,839 ****
  	return ParseVariableBool(newval, "SINGLESTEP", &pset.singlestep);
  }
  
  static bool
  fetch_count_hook(const char *newval)
  {
! 	if (newval == NULL)
! 		pset.fetch_count = -1;	/* default value */
! 	else if (!ParseVariableNum(newval, "FETCH_COUNT", &pset.fetch_count))
! 		return false;
  	return true;
  }
  
  static char *
  echo_substitute_hook(char *newval)
  {
  	if (newval == NULL)
--- 828,899 ----
  	return ParseVariableBool(newval, "SINGLESTEP", &pset.singlestep);
  }
  
+ static char *
+ fetch_count_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("0");
+ 	return newval;
+ }
+ 
  static bool
  fetch_count_hook(const char *newval)
  {
! 	return ParseVariableNum(newval, "FETCH_COUNT", &pset.fetch_count);
! }
! 
! static bool
! histfile_hook(const char *newval)
! {
! 	/*
! 	 * Someday we might try to validate the filename, but for now, this is
! 	 * just a placeholder to ensure HISTFILE is known to tab completion.
! 	 */
  	return true;
  }
  
  static char *
+ histsize_substitute_hook(char *newval)
+ {
+ 	if (newval == NULL)
+ 		newval = pg_strdup("500");
+ 	return newval;
+ }
+ 
+ static bool
+ histsize_hook(const char *newval)
+ {
+ 	return ParseVariableNum(newval, "HISTSIZE", &pset.histsize);
+ }
+ 
+ static char *
+ ignoreeof_substitute_hook(char *newval)
+ {
+ 	int			dummy;
+ 
+ 	/*
+ 	 * This tries to mimic the behavior of bash, to wit "If set, the value is
+ 	 * the number of consecutive EOF characters which must be typed as the
+ 	 * first characters on an input line before bash exits.  If the variable
+ 	 * exists but does not have a numeric value, or has no value, the default
+ 	 * value is 10.  If it does not exist, EOF signifies the end of input to
+ 	 * the shell."  Unlike bash, however, we insist on the stored value
+ 	 * actually being a valid integer.
+ 	 */
+ 	if (newval == NULL)
+ 		newval = pg_strdup("0");
+ 	else if (!ParseVariableNum(newval, NULL, &dummy))
+ 		newval = pg_strdup("10");
+ 	return newval;
+ }
+ 
+ static bool
+ ignoreeof_hook(const char *newval)
+ {
+ 	return ParseVariableNum(newval, "IGNOREEOF", &pset.ignoreeof);
+ }
+ 
+ static char *
  echo_substitute_hook(char *newval)
  {
  	if (newval == NULL)
*************** EstablishVariableSpace(void)
*** 1062,1069 ****
  					 bool_substitute_hook,
  					 singlestep_hook);
  	SetVariableHooks(pset.vars, "FETCH_COUNT",
! 					 NULL,
  					 fetch_count_hook);
  	SetVariableHooks(pset.vars, "ECHO",
  					 echo_substitute_hook,
  					 echo_hook);
--- 1122,1138 ----
  					 bool_substitute_hook,
  					 singlestep_hook);
  	SetVariableHooks(pset.vars, "FETCH_COUNT",
! 					 fetch_count_substitute_hook,
  					 fetch_count_hook);
+ 	SetVariableHooks(pset.vars, "HISTFILE",
+ 					 NULL,
+ 					 histfile_hook);
+ 	SetVariableHooks(pset.vars, "HISTSIZE",
+ 					 histsize_substitute_hook,
+ 					 histsize_hook);
+ 	SetVariableHooks(pset.vars, "IGNOREEOF",
+ 					 ignoreeof_substitute_hook,
+ 					 ignoreeof_hook);
  	SetVariableHooks(pset.vars, "ECHO",
  					 echo_substitute_hook,
  					 echo_hook);
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d6fffcf..6e759d0 100644
*** a/src/bin/psql/tab-complete.c
--- b/src/bin/psql/tab-complete.c
*************** append_variable_names(char ***varnames, 
*** 3775,3782 ****
  /*
   * This function supports completion with the name of a psql variable.
   * The variable names can be prefixed and suffixed with additional text
!  * to support quoting usages. If need_value is true, only the variables
!  * that have the set values are picked up.
   */
  static char **
  complete_from_variables(const char *text, const char *prefix, const char *suffix,
--- 3775,3783 ----
  /*
   * This function supports completion with the name of a psql variable.
   * The variable names can be prefixed and suffixed with additional text
!  * to support quoting usages. If need_value is true, only variables
!  * that are currently set are included; otherwise, special variables
!  * (those that have hooks) are included even if currently unset.
   */
  static char **
  complete_from_variables(const char *text, const char *prefix, const char *suffix,
*************** complete_from_variables(const char *text
*** 3789,3821 ****
  	int			i;
  	struct _variable *ptr;
  
- 	static const char *const known_varnames[] = {
- 		"AUTOCOMMIT", "COMP_KEYWORD_CASE", "DBNAME", "ECHO", "ECHO_HIDDEN",
- 		"ENCODING", "FETCH_COUNT", "HISTCONTROL", "HISTFILE", "HISTSIZE",
- 		"HOST", "IGNOREEOF", "LASTOID", "ON_ERROR_ROLLBACK", "ON_ERROR_STOP",
- 		"PORT", "PROMPT1", "PROMPT2", "PROMPT3", "QUIET",
- 		"SHOW_CONTEXT", "SINGLELINE", "SINGLESTEP",
- 		"USER", "VERBOSITY", NULL
- 	};
- 
  	varnames = (char **) pg_malloc((maxvars + 1) * sizeof(char *));
  
- 	if (!need_value)
- 	{
- 		for (i = 0; known_varnames[i] && nvars < maxvars; i++)
- 			append_variable_names(&varnames, &nvars, &maxvars,
- 								  known_varnames[i], prefix, suffix);
- 	}
- 
  	for (ptr = pset.vars->next; ptr; ptr = ptr->next)
  	{
  		if (need_value && !(ptr->value))
  			continue;
- 		for (i = 0; known_varnames[i]; i++)		/* remove duplicate entry */
- 		{
- 			if (strcmp(ptr->name, known_varnames[i]) == 0)
- 				continue;
- 		}
  		append_variable_names(&varnames, &nvars, &maxvars, ptr->name,
  							  prefix, suffix);
  	}
--- 3790,3801 ----
diff --git a/src/bin/psql/variables.c b/src/bin/psql/variables.c
index 9ca1000..d9d0763 100644
*** a/src/bin/psql/variables.c
--- b/src/bin/psql/variables.c
*************** ParseVariableNum(const char *value, cons
*** 180,210 ****
  }
  
  /*
-  * Read integer value of the numeric variable named "name".
-  *
-  * Return defaultval if it is not set, or faultval if its value is not a
-  * valid integer.  (No error message is issued.)
-  */
- int
- GetVariableNum(VariableSpace space,
- 			   const char *name,
- 			   int defaultval,
- 			   int faultval)
- {
- 	const char *val;
- 	int			result;
- 
- 	val = GetVariable(space, name);
- 	if (!val)
- 		return defaultval;
- 
- 	if (ParseVariableNum(val, NULL, &result))
- 		return result;
- 	else
- 		return faultval;
- }
- 
- /*
   * Print values of all variables.
   */
  void
--- 180,185 ----
diff --git a/src/bin/psql/variables.h b/src/bin/psql/variables.h
index 84be780..1925793 100644
*** a/src/bin/psql/variables.h
--- b/src/bin/psql/variables.h
*************** bool ParseVariableBool(const char *value
*** 81,91 ****
  bool ParseVariableNum(const char *value, const char *name,
  				 int *result);
  
- int GetVariableNum(VariableSpace space,
- 			   const char *name,
- 			   int defaultval,
- 			   int faultval);
- 
  void		PrintVariables(VariableSpace space);
  
  bool		SetVariable(VariableSpace space, const char *name, const char *value);
--- 81,86 ----